Bro those things Unalaq respected are spirits, spirits come in many different shapes, sizes, and forms, they dont all like alike, they don't have to be like koh or wan shi tong all big and important, I dont see what your issue is when the spirits themselves were hardly touched upon in atla and we only saw major spirits IE Koh, Tui and La, Hei Bai,the Painted Lady, Wan Shi Tong, and The Mother of Faces.
The best villains are those that believe they're the good guys and what they think is right or those that are sympathetic, which is what the Korra villains are. Ozai was your typical takeover the world bad guy nothing special.
Amon wanted equality for everyone, something he believed when he was little, the series shows that nonbenders are given enough representation, meanwhile benders are with them having better jobs, are allowed to get away with certain crimes against nonbenders (lightning bolt zolt being a good example), Tarrlokk and his task force, hell Republic City's council was composed entirely of benders, even Korra realized that Amon was right.
Unalaq wanted to bring the spirits back because he rightfully believed that humanity was losing touch with the spirits, for example the glacial spirits festival was supposed to be an extremely hallowed and sacred time, but by the time of Korras era it was just a carnival, keeping the portals closed cased a lot more harm than good, as four or five lifetimes before Korra the avatar was proven to be not very capable at being the bridge between the two worlds, as revealed in the kyoshi novels with Yangchen and Kuruk. Yangchen always sided with humanity whenever they and the spirits came into conflict with one another, leading to many of them to grow resentful and become dark, Avatar Kuruk would learn of this and at the cost of his own legacy, preserved Yangchen's legacy by secretly hunting, battling and destroying dark spirits which shortened his lifespan. The Everstorm which battered the South Pole stopped after the portal was open, Unalaq may have wanted to merge with Vaatu and become a dark avatar, but his belief in the world losing touch with its spirituality, closing the portals was a mistake, and Unalaq was right about it.
Zaheer and his friends though anarchists were right, individuals like Raiko and the Earth Queen were terrible leaders who needed to to be removed just not extremely. Zaheer believed in freedom, which people under oppressive governments and foolish world leaders know little about. Korra herself knew little of freedom since she was locked up and isolated for 13 years and in book 1 Tenzin was restrictive teacher, and she also agrees that that people do deserve just leaders, but the oppressive or moronic ones shouldnt be killed to achieve this.
Kuvira wanted to create a safe place for her people, after it was laced in a state of anarchy and chaos following the demise of the Earth Queen, Su didnt want to take charge, Wu was an incompetent leader, there was literally no one else to fill in the void following the earth queens death. Kuvira however became Hitler 2.O after power as it does with literally everyone sink into her mind and drive her nuts.
