The animation was great once you got used to it. Songs were pretty nice too. I cracked up when they referenced hungry hungry hippos.
But I had 4 major gripes about the plot:
1) The princesses were useless - again. I mean, apparently the magic of 4 alicorns is strong enough to rule the world, but they've done nothing, ever.
2) Where were Shining Armor and the royal guard? An international festival, and zero security duty? Jeez and I thought Hasbro's security with the leaks were bad.
3) Even though the movie apparently takes place between season 7 and 8, I kind of get why newer characters like Starlight and some others weren't written in, but - where was Discord? He would've done anything to help Fluttershy.
4) Lastly, not sure if any others mentioned this, but the world building. World building is great and I love it, but... you're telling me that the Storm King has conquered most of the known world (literally the land right outside of Equestria is under Storm King's control, within a few days of walking distance from Canterlot no less), and no one in Equestria knew about it?? There's no counter measures to a potential invasion?? Is Equestria completely cut off from the rest of the world? Oh but wait, that doesn't make sense, we've seen Celestia interacting with foreign dignitary ponies, such as those from Saddle Arabia (which was mentioned in the movie too). The movie seems to imply that Equestria is allied with the hippogriffs, but they've never been in contact for years? Never knew about the Storm King invasion and the fact that the hippogriffs went into hiding? Never tried to help them out? Oh wait, apparently sentient anthropomorphic creatures are common place outside of Equestria, yet we've never seen or heard of them? Even the ones living literally right outside of Equestria has never seen any of our pastel coloured ponies before. How secluded are Equestria and the other pony nations from the rest of the world?
Unfortunately for me, the world building in this movie fell short. The premise behind the plot didn't work for me.
But as a stand alone, I have to say it was entertaining and I did enjoy it. Just don't overthink it like me and it's a fun watch