Ever since Book 2 ended, Korra has not been an asshole to the people she loves. She doesn't ignore advice and think she knows better than everyone else. She also doesn't take two steps back at every corner.
Quite frankly, I found the way they did Korra's arc (in this regard) to be atrocious. I get logically how they explained it with her being raised in isolation, and people not telling her things. But from a story perspective (how the audience experiences her), it was way too much. And I also am not a fan of how quick the character flipped a switch after the Wan episode (although it was a welcome relief after the BS we went through before).
But Book 3 Korra was totally fine. Whenever she was angry, it was used the way it should be (like the President being an asshole, or that hipster being a dick). And most of her actions in the finale weren't questionable. And she was pretty damn competent throughout the entire season. The ONLY thing you could criticize, is why she didn't go into the Avatar state the moment that they found out Zaheer had lied about turning the hostages over. Because she should have been able to beat Zaheer in the Avatar state (the only reason she didn't at the end, was because the poison was draining her energy). But then again, it's kind of confusing as to whether she can enter the Avatar state at will (after she lost her connection). We do see her eyes glow in the first episode when she soothes the vine spirits. But eh.
I totally get why fans are frustrated with Korra especially in the larger context of the series. But I don't see why anyone should have been so with her in Book 3. She was a great character and was used effectively. And even if you feel frustrated that she's an Avatar that is constantly struggling, I think you should actually find some endearment in that. Not from the failures she caused in Book 1 and 2 from being stupid. I mean the overall hurdles she's had to face (the world trying to move on without the Avatar, he struggle for relevancy, Amon taking away her powers, Unalaq cutting off her past connections and trying to get rid of her, Zaheer trying to remove the Avatar all together). It's a non stop struggle for her to have a place in the world. I think that's a harsh path she has to walk. And I would think people could actually have sympathy and relate to her.
Again, I do get her personal failures early on because of her own actions (and how fatiguing she was). But I do think they have course corrected Korra, and she shouldn't be weighed down by the past writing mistakes.