Anyone who's read Heinlein knows that there are some stories where the race of characters is important and some where it's not. I know this is subjective, but it seems reasonable that the race of actual civil rights icons is more important than that of fictional multidimensional aliens.
Says who? The BBC, for instance, is going to great lengths to replace actual figures from English/British history with people of impossible ethnicities.
Well, it's subjective. The key thing to me is that the character is treated with respect (this is the best way I can put it), and this will vary with subject matter, tone, and media. It's easy for Samuel Jackson to treat Nick Fury with respect in a comic book movie, it would be impossible for a white guy to treat Martin Luther King Jr. with respect in a serious biography. It would probably be impossible for a black guy to respectfully play a Jewish holocaust survivor. This is just the reality of race. As long as it exists it will be central to some stories.
Anyway, consider that these "impossible ethnicities" are British. Idris Elba, for example, is an incredible classically-trained actor born in London. What roles in the predominately white history of Britain should he be excluded from? Should he only play African thieves like in his first role, or a made-up African prince visiting Henry VIII or something? He's a Shakespearean actor - should he only be able to play Othello?
Maybe one day we'll figure it out, but it seems to me it'll get more complicated as ethnicities mix. What if Tessa Thompson was half-Norwegian, for example? Would she be less suited for the role of a Valkyrie than a blonde from Iowa?
Actors very rarely match the background of their characters perfectly. We've always had chiseled guys playing dumpy kings, 30-year-old English women playing French teenagers, accents are all over the place, some characters are composites, whatever. Skin color really isn't a deal-breaker for me in historical dramas, and especially not with minor characters in comics.
But like I said I might feel differently about serious biopics than fluffy historical drama. It's subjective.
I also seriously doubt there's a "Great Ginger Erasure" because red hair is vastly more common in cartoons and comics than in reality. For some characters its an important part of their identity (Red Sonja, for example), for others its just because red is easier in printing and it's a bright color that contrasts well and easily distinguishes flat background characters. In others its just a visual shorthand for feisty woman or nerdy kid. If changing the weird orangish-mustached guy with a heart on his chest to a black kid in She-Ra threatens any grown man's identity they probably have a serious problem and should take immediate steps to get laid.
Anyway, I like science fiction. I like history. I like other people to feel included because it's more interesting people for me to talk to about these things. Disney likes people to feel included because it makes them more money. If this is woke I don't really care, I didn't even know tumblr was still around.