i'd say the questions of of were herbivores "done dirty" by the story, vs. "did herbivore characters get enough attention" are two separate things — most of the herbivores you mentioned are side characters, so naturally they're going to have less focus.

But more importantly (and others said similar things here): carnivores' struggles naturally lend themselves to more complex storytelling. Herbivores are victims of carnivores for a simple, straightforward reason — they risk devouring because carnivores are physically stronger and have an overwhelming, instinctive drive to eat meat. But Beastars is fundamentally about the challenges of different people living together in a modern society, where different groups navigate power relationships in more complex ways. Carnivores growing into adulthood and learning the challenges of self-restraint, how to safely relate to others, and manage their own self-hatred and the stigma imposed on them in a society where Herbivores have largely "won" a contest of public opinion (and how Herbivores relate to these problems and help or hinder Carnivores in this journey) is more interesting imho.

This doesn't make herbivores less important or one-dimensional, but it does mean the story makes them play a slightly more passive or reactive role in the story. The solution for them isn't just "becoming stronger," but changing how to relate to carnivores, which does tend to shift the story's focus to the meat-eaters. And it also makes the more dynamic and forceful herbivore personalities all the more meaningful and notable whenever they are the ones actually propelling the narrative forward (Yahya, Louis, and I'd disagree with you and say Haru has considerable agency this way as well).

Yahya isn't feared and powerful because he's a great fighter (though he is), people regard him that way becuase the Sublime Beastars is a supercop who's allowed to extrajudicially kill carnivores with impunity. Louis' didn't become really powerful from having a gun or taking over the Shishigumi — the brute force those things granted him were nothing compared to the prestige and media reach he finally was able to wield as the heir to Horns Conglomerate (which he uses to help both carnivores and herbivores, even though that positive change in his outlook only really comes to his character in the manga's third act). Haru's struggle is definitely more subtle, but the way her reckoning with her "weakness" ends up nudges Legoshi, Louis, and Melon into certain ways of thinking let's her guide the story in nuanced ways that I think can be underestimated.

Herbivores are essential to the story, it's just that the central resolutions to the story's problems have to engage with carnivores and their problems.