LoK was more ambitious than ATLA and I think it should get praise for that. I actually enjoyed the rotating villains more than Ozai, although none of the villains reached the level of Azula in terms of how compelling they were.
The real problem with LoK is it had no fucking idea what to do with the characters. I didn't dislike any of the main cast but Michael and Bryan just seemed to meander around with basically everyone in it. Bolin is a probender, oh wait, now he's an actor, oh wait, he can lavabend, etc. It's like they have no confidence in his character and don't even get me started with Asami who is basically a non-character. She doesn't do ANYTHING. She's wasted opportunity the character. And the whole Korra-Bolin-Mako love triangle got really tiresome because the guys have no fucking idea how to write good romance. It was just.... bad. And Korrasami makes no fucking sense. They have what, like one kind- of sort-of romantic scene together before they go off at the end? There was zero buildup and /co/ is right to be mad about that shit.