First, we gotta establish what's wrong with the current one. I'm just gonna copy-paste what I had already written down before and put it here. No point in rewriting it every time.

It’s a fun, OK film, but definitely not a masterpiece.
The film has so many unanswered questions and plot conveniences, most notably The Storm King. He’s just suddenly there, even though we’re supposed to believe he took over tons of land before attacking Equestria? Same counts for the anthropomorphic animals (very out of place design too, in my opinion) and sort of the Seaponies, but that’s only less so because the fandom saw it coming before the film was even out. They’re all just there, as if the world this takes place in is a different and bigger one than the show.
The Storm King is also a bad villain in general. Next to the fact that he has no origins, is he also extremely 1 dimensional. He just wants power because he seeks it, and the only personality he has is the standard, witty yet mean bad-guy.
Tempest does go through a good character arc, though not a very original one for this franchise. The way it was pulled off was decent, but I especially like the motivation she had. It wasn’t just ‘I hate friendship, I’m against it!’, it was ‘I don’t care for friendship, I’ll only destroy it if I need to.’ That wasn’t something we saw before the 2017 film.
The rest of the characters had just ‘eh’ arcs, though. I mean, Twilight went through tough stuff (the fact that the last two words rhyme but through and tough don’t is crazy, isn’t it?) but nothing she couldn’t handle, and the rest (apart from Pinkie) were hardly doing anything in this film. Capper had a good arc, but in the end it just felt kinda, I don’t know, unnecessary? Or maybe wasted is a better word? He helped break in into the castle, but was all of that character development just for that? Felt to me as though he was done a bit short. Still very enjoyable, of course.
I liked Pinkie, though. Especially the scene where she and Twilight get in a fight. It’s not something you’d expect Pinkie to do, asking to break contact for a bit, but Twilight hurt her so much she does it anyway.
In the end most parts of the story seemed a bit forced, as if the writers were trying to expand the lore but didn’t know how to and just made an entire film for it. The entire film was in the end just to expand the Cutie Map, and thus it felt really unnecessary as well.
Mind you this doesn’t mean the film isn’t enjoyable. It’s funny, very beautiful like you said and the score is fantastic. The fact that the MLP staff even wanted to make a film is also an amazing thing, albeit that the film isn’t very great.
I’m glad you enjoyed it, I did too (aside from the occasional ‘why?’s’ I had during the film). Thank you for reading if indeed you read all of this. T’is a bit lengthy, isn’t it?