My sister and I have come to the conclusion that the story suffers because they are simply trying to make the proverbial lightning strike again by recreating popular characters and emotional beats. Lith mention the obvious Cor = Auron reference but there's plenty more.
They desperately want Ardyn to be a new Kefka. And he's not. He's not a terrible bad guy but he's no Kefka.
Iris is the cute kooky girl next door, Selphie comes most to mind for me.
Cindy is tits and tech = Jessie, Tifa, etc.
Cid is... well Cid and I really love this version of Cid. Straight up he is one of my new favorites.
Iedolas is severely underplayed in the game but they were going for a Maester Mika or Emperor Gestahl and again missed the mark.
Aranea is a nice combination of Lightning, Celes, Leon and Kain.
Now let's talk about the forced, rushed emotional beats.
Hey kids, you loved Aerith's death? Let's have Lunafreya die. Yeah it had weight and was foreshadowed, but I'm convinced that's the only reason it's in there. The Lifestream-esque dream sequene at the end recreates Aerith falling into the abyss which is pretty powerful imagery (just ask Pixel
)
Hey kids, you loved Tidus's self-sacrifice at the end of X? Well guess what Noct is going to sacrifice himself to save the world. Again, this was foreshadowed very well, particularly with Kingsglaive. Also side note, most people seem to be under the impression that the other three bros died as well. I mean I can see it, they were in the afterlife too, but if that's meant to be obvious they conveyed it incredibly poorly. I thought Ardyn just knocked them down, not killed them.
Hey kids, you like when we add suspicious character motivations like Kain, Rikku, and Celes? Well Prompto stupidity that we will do absolutely nothing with and doesn't inform the character at all and is immediately resolved!
Hey kids you love massive city destruction like Kilika? Well boom Altissia!
They tried very hard. They tried too hard. And the story suffered immensely for it.