I can illustrate one way that "diversity" hiring has affected perceptions of a demographic. In the 1980s, I worked around engineering departments a lot. Women were rare, but it seemed to be widely assumed that any woman in engineering would be exceptionally capable and driven.

These days, when I hear discussion about inclusive hiring, regardless of whether people are for or against it, there is a common assumption that allowances will have to be made for employees of lesser ability.

My impression is that this change in attitude started in the mid-1990s.