I don't think "appropriation" is the right way to frame this question. It's really about failures of the imagination. It is possible for an author's imagination

I don't think "appropriation" is the right way to frame this question. It's really about failures of the imagination. It is possible for an author's imagination to fail whether or not they share a group identity with the subject of their fiction; i.e. there are lots of bad writers. Certain kinds of imaginative failure are specific to people outside of a group writing about that group (these failure modes tend to deal in stereotypes and sometimes propaganda), but that doesn't mean they will all fail. So the easy filter of "author Y is not X, and therefore should not write about X because X will be misrepresented" doesn't stand. The second objections seems to be about market failures: "author Y is not X, and therefore is taking an opportunity from authors who do belong to group X." Personally, I don't think art is zero-sum. I don't believe that, for every book that was published by a well known author, a lesser known author was rejected. And I'd like to point out that, while publishers may still be important, we live in an age when artists can publish their work online and go directly to their readers. Those that build a following will get picked up. Those that don't may use that feedback to reflect on their style. The urge to write doesn't guarantee anyone a living.