Mostly it comes down to emotional set-up and payoff. This film lacks it in so many ways. One could argue that to some extent none of the Middle-earth movies were built to stand alone. Now, that wouldn't be true, but one could argue it.
Each film in "The Lord of the Rings" trilogy stands on its own just fine, and despite all three forming a large, overarching story, each feels like it has its own conflicts and resolutions. The first movie in this newer trilogy, "An Unexpected Journey," succeeds in this as well. For its part, the second, "The Desolation of Smaug," largely prevails -- right until the closing credits begin to roll anyway, and that's right about the time the problems plaguing "The Battle of the Five Armies" begin.
Right from the start, we're treated to a resolution that feels like it belonged to the second movie, and should have been its emotional payoff. All the dangling threads of tension from the last few minutes of "The Desolation of Smaug" are rapidly addressed in the first few minutes of "The Battle of the Five Armies" -- before the film's title card even appears, in fact.
If that isn't the perfect summary of why those opening minutes should have been the closing minutes of the previous film, I don't know what could encapsulate it better.
We have Bard the Bowman's escape from imprisonment, the frantic departure from Lake-town of his children (accompanied by Tauriel and the Dwarves left behind in the previous movie), Smaug's brutal attack on Lake-town and the dragon's unexpected (if you haven't read the book anyway) death at the hands of Bard -- all tense plot threads that were boiling over in the closing minutes of the previous movie! Which will forever be deprived of a proper close thanks to these absolutely baffling, disjointed choices of pacing.
As said, none of these moments get to carry the emotional payoff they deserve, as their set-up lay in another movie. One which many of those watching will not have even seen for a year. Even for those who have seen it more recently, the flow of the storytelling feels awkward through no fault of their own.
This awkwardness carries over into the final battle between Thorin Oakenshield and Azog the Defiler as well. We haven't seen the animosity between these two fed since the first movie, so it almost comes out of nowhere when Azog forces Thorin to watch as he executes the Dwarf king's nephew, Fili. And just like that, we're watching Azog and Thorin fight to the death in an extended sequence that may be the single longest involving any two characters in the history of all the Middle-earth films.
Even worse is the showdown between Legolas and Azog's son, Bolg, that occurs concurrently with that other battle. Here, the film attempts some resolution to the rivalry of sorts set up between these two in the previous movie, but it just ends up feeling like Legolas is interfering with the emotional set-up of this film by battling Bolg to the death when it was Tauriel's beloved who had just been murdered by him, and when it was Tauriel who has been fighting Bolg in this movie.
By virtue of both most recent set-up and the greater grievance, this was Tauriel's fight to finish, and it should have ended when she sent herself and the Orc over the edge of the battlement where they had initially come into conflict. Perhaps that should also have resulted in the death of Tauriel along with Bolg for all that ends up being done to resolve her personal subplot of love and loss; perhaps not. In either case, ending Bolg's involvement in events there was the best -- maybe the only -- opportunity for emotional payoff and narrative satisfaction that would be afforded by his inevitable death, and the movie blew it.
After that, as it became increasingly clear this would be Legolas's kill, I became increasingly disinterested in the fight and kept wishing for its rapid resolution. Which brings us to highlighting another problem the finale to "The Hobbit" trilogy bears in spades: One-on-one fights that last way too damn long.
Not only do they feel inconsistent with the more epic skirmishes of the original trilogy, wherein our superhero-caliber protagonists would face down a horde of foes, these bloated sequences consume precious screentime. Time that would have been better served either providing a more panoramic view of the larger conflict (whose scale is almost immediately forgotten by the unending focus on no more than half a dozen warriors at most) or giving more exploration to characters who had been with us from the beginning of this trilogy, yet for a number of whom this movie didn't deign to even given a single uniquely identifiable line of dialogue.
Most of the Dwarves who have been with us since before Bilbo left the Shire are interchangeable scenery dressing -- far more so than in the previous two films. Of the 13, I'm only sure five of them have any moment where they occupy an appreciable amount of the camera frame, are mentioned by name, or actually speak in something outside of a group shot where it doesn't matter who said the words.
Even Bilbo himself, despite being the eponymous Hobbit the trilogy takes its name from, often feels like a guest role. I won't go as far as to say he may as well not be there, but I will say this movie was no longer about his journey the way the previous two films were, and that it lacks the benefit of a central character to anchor it the way every other film in the Middle-earth series had.
Again, it would be inaccurate to say it would be just as well that Bilbo not be there, but it would be entirely accurate to say the film lacks a point-of-view character to latch onto. His loyalties may not go unexplored or his courage without demonstration, but if he learns anything new about himself, we aren't privy to the discovery. Instead, he comes off feeling entirely too capable after what we have seen of him up to this point. He no longer feels like an unsuspecting player out of his depth and caught up in world events beyond his scope. We lose our ability to put ourselves in his shoes (i.e. his big bare feet), and no one else emerges to take his place.
Instead, we get plenty of time devoted to Luke Evans's Bard the Bowman competing with Orlando Bloom's Legolas in an attempt to prove who can stare off screen more intensely and speak in the most weighted tones (for the scene where they were on screen together conversing, I had doubts the projector could handle the strain). Even more unforgivable is all the misused attention given to the constantly annoying Alfrid, who could have fulfilled his narrative purpose at the beginning when Bard convinced the people of Lake-town to spare the ingrate, yet he continued showing up at periodic intervals to prove he was no better for being granted mercy than he had been prior.
At the least, there should have been some resolution to his arc if this much time had to be wasted on him, but -- even less so than Tauriel, who is left crying over Kili's body with an unanswered wish on her lips -- we get nothing to resolve his role or justify his ongoing presence. Just periodic annoyance and more missed opportunities to develop the relationship between Thorin and his nephews, or between Kili and his brother -- you know, something to give added weight to the cruel execution of Fili, who I'm not sure says more than two sentences in the entire movie before he gets skewered.
No, though. Let's instead give all that time to a failed comic relief character who merely annoys everyone both on the screen and watching it, and who, if anything, only succeeds in upsetting the tone of more tense situations and further derailing the already wayward pacing of the story.
Whatever time is left? We'll give that to a couple of one-on-one battles that last way too long. Maybe we'll check in on those five armies mentioned in the title card before we roll to credits.
Seriously, though, those fights were too fucking long. It's not even like that was necessary. Aragorn and the Orc chieftain Lurtz had an exhilarating one-on-one in the final minutes of "The Fellowship of the Ring" that lasted just under a minute, but was nevertheless intense and still showed off the battle prowess (i.e. how badass they are) of both warriors. For its more effective use of time, I would even argue it was the most memorable such fight in either trilogy.
I won't take the road a number of other reviewers apparently did and condemn the time spent on Thorin's Dragon Sickness, but I will say it came upon him too abruptly. Beyond the moment in "The Desolation of Smaug" where it seemed he was threatening Bilbo before battle with Smaug commenced (a moment likely forgotten by many viewers), it almost feels like Thorin hasn't gone mad so much as chosen to just be a dick.
There's really no problem with the time given to the Dragon Sickness. Instead, the problem is that the time is poorly allocated. Thorin has no fall; no descent into madness. He's just suddenly different, as if under a spell. We don't even see him struggle to fight it. His redemption is equally abrupt. There's no real catalyst for his recovery. He just suddenly gets better after experiencing an unexplained acid trip of sorts.
To his credit, Richard Armitage -- being the amazing actor he is -- pulls it off well enough so as not to let it do all the hurt to the film it could have, but a lesser man in the same shoes would not have carried it. Armitage, as before in "An Unexpected Journey" and "The Desolation of Smaug," is one of the joys of of the film.
Add to that category, too, Martin Freeman's Bilbo (like Armitage, making the best possible use of what was given to him) and Lee Pace's Thranduil. The aloof Elven king is surprisingly human and ultimately honorable, even if the resolution to his impetus for getting involved in the war is yet another dangling plot thread lost along with the fate of the Arkenstone that Thorin so desired, where Tauriel goes from here, whether Alfrid found honor or the tip of an Orc spear, what became of the Dwarf army, and how the treasure of the Lonely Mountain was divied up.
Shockingly, the White Council's assault on Dol Guldur and rescue of Gandalf is -- in addition to being one of the most awesome sequences in all the Middle-earth films -- one of the more appropriately resolved. It ties "The Hobbit" trilogy into "The Lord of the Rings" very well, and more than convincingly displays why Galadriel, Elrond and Saruman are regarded as the important figures they are. Yet it's disheartening that a scene from the film not even featured in the actual book (it gets a mention in passing toward the end) is one of the more deserving of accolades.
This scene, coming early in the movie, also serves to highlight the problems with it demonstrated by the opening sequence with Smaug's attack on Lake-town: It feels like the resolution of set-up from the prior film, and there is too little of it to justify its presence being found here.
In a great many ways, the length of this so-called "defining chapter in the Middle-earth saga" could -- nay, should! -- have been lessened. Perhaps even the overall tale compressed but to two films, as Peter Jackson originally planned. This could have been done. It didn't have to be, but with such poor choices made in what to do with the extra time offered by having a third movie -- the unnecessary inflating of battle scenes that didn't require it and sub-plots that went nowhere; the squandering of character relationships and personal struggles that are left gasping for air -- it may have proven more conducive to bringing out Jackson's artistry.
Working to compress all of "The Lord of the Rings" into three films brought out his best and let him create a masterpiece. It's a shame that the opportunity for self-indulgence led him to make something merely serviceable. Not a failure, no, but far from a triumph that will call you back to Middle-earth again and again for years to come the way the prior trilogy still does.