Before playing this, I thought people disliked this game because it was too gimmicky. (they probably do, but it's not why I dislike it)
turns out the real reason it sucks is because it's not gimmicky enough.

the combat has some great and cool ideas, but it mostly falls apart when you get access to a lot of high value cards, at which point you can ignore most mechanics for most combat encounters and basically buttonmash your way through, turning the game into a watered down version of the first game.

maybe some later bosses made it more interesting (in fact, the first couple bosses were great, when my cards were still low value. the game could have been good if more of it was like that), but that doesn't forgive 90% of combat encounters being uninteresting.

also, don't get me started on map cards. basically means you HAVE to grind to progress if you get unlucky, or used a map card you needed later without knowing.

all the worlds being from KH1 with the side stories in them also being almost copied from them doesn't help either.

the main story is great though (and important to the series), so just watch a cutscene compilation online.