And lets face it, Zaheer did more for changing the world then Korra was probably going to do.
No Zaheers just fucked things up. Korra reunited the Physical and spirit world. She literally changed the what the world works.
The Earth queen needed to go be Zaheers did it in the most retarded way possible.
No Korra added pokemon to the world and made trees grow. (Because the show does a really bad job of actually showing what spirits actually do)
Zaheer fucked things up, but at least it forced people to actually looked at what was happening.
Also the entire Amon thing was poorly written, because they actually try to set up the Non-benders were being mistreated then dropped it. Making you wonder what the entire point was? Though It really wasn't a surprise since at this point you honestly wonder why non-benders are even in the show. Asami is shown to be the only capable one, and even then it's more because she's rich then anything else.
Plus, Aang was acting as protector of the city, when he died everything went to shit. Remember, after Sokka there was no non-benders on the council. Let me repeat, a large majority of the people weren't even represented at that point.