I find it really interesting. I get the argument about levelling the playing field for actors of colour - that's fair enough. In some things, like the film of David Copperfield, I find it pleasing; in that instance it totally melds with the director's political message (about inclusion and diversity and celebration).
I do think it has some downsides though. Not everyone has a thorough grounding in what societies were really like in previous eras, and I think we might be creating a confusing impression about the impact of prejudice. (A PP says 'you know that's not what it's doing' or words to that effect, and it's interesting to see that explanation because I hadn't heard it before. It feels of a piece with a lot of what I find intellectually dishonest about post-structuralism.)
In the same way, the current Sky adaptation of Amadeus shows lots of women playing in the orchestras in early nineteenth century Viennese opera houses, which just... wouldn't have happened. It wipes away the reality of the impact that prejudice had in people's lives, and that does bother me. It's important to understand that people of colour and women had highly circumscribed lives. That was a thing that really happened, and that affected millions of people, and shaped the nature of those societies. If you smooth that stuff out and pretend/imply it didn't happen, it's very, very difficult to understand anything about how those societies operated and how world events played out.
I feel like in Copperfield (the movie) it was doing something narratively important and intentional, whereas in some other productions it's a more intellectually coercive/dishonest imposition of modern norms - it feels more like 'just pretend you believe that 2+2=5 even though we all know it doesn't'.