Having worked in Hollywood, I can say that this is a very tough area for equality because of the stakes of it all. There are only 8 major studios and thus 8 studio heads in all of Hollywood, and for the past 10 years it’s very possible to get fired for bombing once.
In a job where execs can’t make a single mistake, with a mistake meaning to make an unprofitable movie, talent isn’t even the most important thing. Making money is. Will Smith is black and was the top actor in Hollywood for years because after Leo made Body of Lies, he was the only actor to make his film budget back during opening weekend every single time, until he made I Am Legend. But you can see that since he bombed in I Am Legend, he isn’t appearing in much for unknown reasons.
All this is to say, Hollywood execs will cast whoever they think will make money. If top white actors make more money, they will likely be cast more. The studio heads’ career stakes are too high to take risks. Hollywood execs openly admit to passing on deals because they ‘aren’t in the business of taking risks’ (Paramount on passing on the Netflix Scorsese movie).
I also feel like with everything today being a franchise, sequel, reboot or based on source material, if the original characters were white, it can limit the choices. I for one would like more original screenplays and alternatives to a $30mm marketing budget. This would allow for more diversity.