Your problem is that you fail to understand that autism isn't a disease, it's a neurodivergence, their brains are just wired slightly differently. Many autists live their whole lives without even suspecting of their conditions, and most of those who are aware of it live absolutely normal lives. The only way we could potentially "cure" autism is if we somehow altered peoples' brains while in the womb, if that's not eugenics I don't know what is.