> which is the bigger problem for those groups - having those unrealistic role models, or not having them to begin with?

I think they're probably both a problem, but the latter seems to get talked about and somewhat addressed, and the former not so much (not at all in fact, afaik). My (tentative) hunch is that letting people know that it's supposed to be hard and you're supposed to struggle might result in more non-white-male people making it into STEM than more minority wizard characters.

I feel like that's the kind of nuance you learn as you get older. Black Panther might inspire some pre-teens to start down the path to science, and someday they'll probably see October Sky or whatever the current equivalent is.