The film Arrival (2016) is well known for hiring consultants- experts in linguistics, other scientists, even Stephen Wolfram- to improve its portrayal of an alien language and the people working to decipher it.

Nobody complains when a consultant is hired in this capacity, and yet sensitivity readers, whose role is broadly similar, are somehow considered bad? It's not like they rewrite your whole book- they offer notes for things that don't make sense given the characters and plot, just as a developmental editor might.

A publisher doesn't just print the text they're given, they edit it, suggesting changes they believe will help it be better (and thus sell better). There's a back and forth dialog between editors and authors, and it's entirely possible either side might walk away if there's no willingness to compromise. This happens to all books that aren't self-published. Adding another type of editor to the mix isn't gatekeeping.