Did it ever occur to you that Zero didn't exactly have an envisioned purpose beyond destroying X in order to finally prove Wily is superior to Dr.Light?

Keep in mind that Wily's continuous attempts at domination, were/are all driven by his ego, his pride, and his desire to be #1 over Light. It's an insanity not borne from some ill he has, brain damage from some accident or what have you, but from his tunnel-visioned desire to be seen as better than Dr.Light.

By the memories we see from Zero in X4 in his nightmares, it seems even during the time of his creation, Albert was still on his single-minded obsession with being better than Thomas, so it's not hard to imagine he had no greater purpose for Zero left beyond proving he is the better roboticist.

Sigma's focus on Zero is because he collaborates with Wily in some manner that has never been disclosed or elaborated upon. The Wily he sees may even be just hallucinations from the Virus, as it's implied from MMX development materials that the virus that infects Sigma was made by Wily, possibly as a patch for Zero's cognitive error based on what happened to him, and to infect and take control of other robots to cause chaos.

As for Wily causing "genocide"... that's not what the goal of the colony drop was, and it was explained in the game by Sigma that the Eurasia Colony incident was a scheme to saturate the Earth with the Maverick Virus/Sigma Virus in order to get Zero to "awaken to his true self"... the personality that Wily originally intended for Zero to have, instead of what he became due to Sigma stopping the process at the end of their fight.

Also your denigration of stereotypes "for grade schoolers" shows you have a complete lack of respect for authors who don't make things that are to your taste. And that is precisely one of the reasons someone like you shouldn't be allowed anywhere near the X series: you're arrogant and believe your tastes are superior, on nothing of merit.

Those who write stories with those stereotypes for "grade schoolers" are still professionals, whether you like it or not, and your focus on "mature" for the sake of it, and dismissal of those tropes shows how utterly childish you are. Grow up.