People dislike Dragonite...?
I could be wrong here, but I don't think it's so much that people dislike Dragonite. I think it's moreso some people prefer Dragonair and wish Dragonite looked more like it. It
is a pretty drastic change, after all. I don't know if that's what the OP is referring to, but I have seen that opinion thrown around in some corners.
I'll throw out a couple myself.
Delphox is probably one of my favorite Fire types, which is why I was completely crushed when I saw literally everybody trashing it when it was revealed. Granted, it may be because it's 3D model is pretty unflattering, but I still saw many people disappointed it didn't retain the whole "magical girl" look Braixen had (and honestly, I never really cared for Braixen too much; it's too cutesy and girly for my taste). Probably didn't help that Greninja completely stole the show in Gen VI and pushed both it and Chesnaught into the background. But 3D model aside, I absolutely love Delphox's design and think the whole mage concept is creative.
Also, while its design took some getting used to, I'll throw out Alolan Persian as well. While I do prefer Kantonian Persian, I can understand why they went in the direction they did with the Alolan variety, especially since it's supposed to be based on a British shorthair, which are pretty goofy looking cats to begin with. I think what doomed it is that Kantonian Persian has this very sleek, elegant design that people were expecting the Alolan variety to retain, but instead we get this goofy looking cat. But IDK. I kinda like the contrast.