While the story is more interesting than "go defeat Firelord, he's evil because fire", it also lacks focus. Not every season needed to have a completely new villain, it just kills the momentum to have everything miraculously wrap up after each season. The ending to the first season was a total shock as I expected the plot to span all the seasons, but every plot thread just got wrapped up in the span of an hour. What?
What really hurts Korra though is the cast of characters.
Team Avatar: Mako is just a boring asshole, Bolin is a clown, Asami feels completely pointless. Don't even get me started on the useless animal/spirit mascots. There is no feeling of pure friendship between them like before, because the stupid love-triangles (plural if you count Bolins pointless romance subplot) constantly get in the way. They feel completely useless. Team Avatar is not needed, because unlike Aang, Korra is a full avatar. It just feels hollow. Where is the caring nature of Katara or the undiluted awesomeness of Toph?
Team Airbenders: I give Tenzin a pass. I feel he's actually grown as a character and I kinda wanna see him do more stuff. Jinora had her deus ex machina moments, but otherwise his entourage of kids is just annoying (especially Milo. Fuck off, Milo.). His wife has yet to justify her existence in this show. Basically the only noteworthy thing she did was give birth to a pointless baby. Is she just background noise? Bumi is just another clown character, but since he often appears in the same places as Milo it makes me wonder if they're supposed to be competing for my hatred. I even forgot the name of Tenzin's sister and that one airbender kid, because they're so uninteresting.