I think Steve Sailer had the correct take on this: there will always be roles for white men in Hollywood, if for no other reason than that somebody has to play the villain.
Oh yeah, of course they'll still play the token racist villain, there might be a few token good Asians or Hispanics too, but say good bye to good guy white male protagonists at this rate.
It's a problem because it's boring because it's overdone and becomes samey after a while, once upon a time it was interesting to have a movie star be someone like Will Smith or Denzel Washington but now it's boring because 90% of actors in media today are black and black characters are not allowed to be interesting, they're not allowed to have any character flaws, which is a big part of what makes a character interesting, it's always "strong and competent" ie boring as shit, Captain Marvel being a female example.
To use an example of a white male character look at Indiana Jones, he gets his ass kicked constantly, he has phobias ("I hate snakes"), he has daddy issues, he is in other words written to be human enough to be interesting despite also being a larger than life action hero.
You can literally list good characters and their flaws all day long, Tony Stark being another example, he's brash and overly confident which sometimes gets him in trouble, at the start of his first movie he's actually a total asshole and has to be humbled and work his way back up to being a hero, again I have to cite Captain Marvel as an example of the polar opposite, there's nothing human about her and consequently nothing interesting, she doesn't have to be humbled and work her way back up, she's perfect from her first scene.
It would be just as boring if it was nothing but white people and white characters were also written to be as bland and boring.