There is a huge difference between the different "eras" of FF games due to the technology that went into creating video games at the times of their making. So certain things were easier to do or take advantage of in different FF games.
Like... before voice-acting, it was a lot easier to cram in more text and have longer stories. Sprites require a lot less man-power to devleop and animate compared to modern 3D assets. The story needs to be developed far in advance in today's video-game creation pipeline so that all the assets can be created, while that wasn't as important back with the first FF games were made. So the way Final Fantasy can dazzle people has changed.
You also have the problem of getting new developers to create FF games. The older generation of FF devs don't seem to have made the jump to the scope of modern game development as well as some of the younger generation has. And at some point, we need different people making FF games then we used to, or the series will die.
One of the big problems all the Final Fantasy games have (I think) is that their developers are really bad at knowing when to stop creating ideas for the games. They have huge sprawling worlds and worldbuilding and plots. Back when creating assests wasn't as involved as it was today, that wasn't as much of a problem. Nowadays, it is though. Needing huge worlds and lots of exposition is a lot harder to do now whith all the 3D modeling and open-world type of gameplay. Back when the world map was represetational instead of literal, it wasn't as hard. And I don't think Final Fantasy has made that transition very well.
All you need to look at is FFVII's setting scope verses FFXII's (and the later titles after FFVII). FFVII's setting is huge. It's the entire world. FFXII is like... two continents on that world since the map isn't representational anymore. However, it doesn't feel like the story scope was adjusted to fit the smaller setting. There's good reason why FFVIIR is being made in three games. And I think it's largely that the kind of story told in FFVII can't be told over one game anymore.
There's reasons why I'd say FFXIV has the best story out of the Final Fantasy series in over ten years. And a lot of it is because it's a serial game. Instead of having to come up with the entire story all at once, the devs have been able to pace themselves and put ten years worth of story-telling in one game and then reference it all whenever they want. You've got plot lines from 1.0 that finally get tied up (or at lest explained) in 5.0 which is... ten years later. You can't do that kind of long drawn out stories in one game anymore, if only because the size would be imposible to do with today's gaming standards.
TLDR: Making complex stories in video games is harder then it used to be I think. At least when it comes to the type of stories Final Fantasy is used to telling. Final Fantasy has gone through a lot of growing pains figuring out how to tell the kind of stories it used to in today's video-game technology. I think they are finally getting the hang of it, but really, only a new Final Fantasy mainline title will prove if that has happened. FFVIIR is a great step in the right direction though, because it lets Square Enix take a story they know worked very well and see how it would work with today's video-game technology. That way, they are more experimenting with how to tell a story, rather then what kind of story they are all ready telling.
Unless we're talking about the Final Fantasy MMOs... which figured out what they should be doing in the modern era long before the single-player Final Fantasy games did. Which I think says something about the Final Fantasy series as a whole. The scope of Final Fantasy worldsp (at least in the modern era) fits the scope of MMOs far better then it does modern single-player games.
, Skyrim) really delivered on a higher level. While unable to regain the glory of old and despite its flaws (especially in the story-telling department), I think that FFXV was definitely a step in the right direction.
