There's a lotof nuance that people seem to leave out or flat out ignore in these situations. It just leads to the same arguments over and over on repeat because no one can hear the other side out when they're wrong because they want so bad to "win" on the internet.
I've seen the argument that this situation only blows up if the character is made black and that's true. No one was mad about Mamoa being Aquaman. No one was mad that Ben Kingsley was the Mandarin (until the twist). Tom Hardy as Bane. Etc. Etc. But when characters are made black there's always a vocal pushback.
We've seen the argument that if it was the other way, people would be called racist. Like making Black Panther or Shaft a white dude. That doesn't work because being black is 100% a part of their character.
Another thing people say is, "just make new black characters." Problem with that is you're probably not gonna get a major return upfront. Gotta spend money to make money but still. And I know Black Panther exist but that's Marvel so it was sort of a guaranteed billion.
But the big one that a lot of people seem to leave out, is that if a lot of these characters remained white all these years and decades later, you would be leaving most all minorities out of major starring roles in billion dollar franchises. Lord of the Rings and Harry Potter, primarily white cast all the way through. And there are even more franchises that are at that level. But again, most all those roles are "whites only." Life changing money but not for those of us with pigment. Same with a lot of Oscar roles. Hell, remember Oscars so White?
If you take a step back and just look around you'll see just how much is still white. But they'll always be those arguing about erasure just because 85% white dropped to 80% white.