We’ve seen that happen with using “gay” as an insult - society has shifted over the years, so that being gay is no longer seen as a bad thing

I don’t remember that “just happening”… I remember prominent members of the homosexual community deciding to reclaim the word “gay”, and then working to bring the more neutral connotations into the mainstream - and that effort is still ongoing.

The people targeted by the slur had to have the resources and ability to change public perception before that could happen, and it took a considerable, concerted effort. It did not just “shift”, and that process is not equally available to every target of a slur.