The tricky part is that even if the source material has no non-white people in it, the real world does and representation matters.
If you cast diverse actors, you are less precise, but are making the world a (slightly) better place for underrepresented and disadvantaged people. If you don't, you are more precise and are making the world a (slightly) worse place for underrepresented and disadvantaged people.
You put me in a difficult position. I don't really watch movies anymore ( Joaquin's Joker was ok ). I rarely get into shows ( I was amused by Boys ). I still read a little. That said, I can absolutely guarantee you that never have I ever in my entire existence on this planet read something and thought to myself "If only Geralt was black, or at least a gypsy, the world would be a better place" for several different yet related reasons:
1. It is supposed to be my entertainment and not a social project ( or more accurately, it can be both, but entertainment should be the primary consideration; after all, if I pay, I expect some value )
2. I do not accept the assertion that it does make better place for underrepresented and disadvantaged people. Right now, it is actually making it worse. You may not be seeing it, but counter-culture is rejecting it pretty hard and that is with all the internet censorship in full swing ( granted, currently for corporate reasons, but censorship is censorship is censorship ). If anything, this hamfisted approach creates a whole new generation of actual racists.. I do not think that makes for a better place for "underrepresented and disadvantaged people".
I don't buy the binary framing either. To me, neither is important.
Things are inseparable. I mean you can write shallow stories, but anything attempting to map realistic worlds to fictional ones is going to have conflicts including those that are considered 'politics'.
The crux should be the writing, immersion, and ability to be invested in a story with these things.
I mean, Tolkien is dead. Shakespeare is dead. Homer is dead.
We can't make more Tolkien, Shakespeare, or Homer. We can just put our own spin on the stories they told, retell or reinterpret them as we see fit. The "most faithful" adaptation of their stories to the screen is still an adaptation.
If you enjoy the original works ... enjoy the original works.
If you cast diverse actors, you are less precise, but are making the world a (slightly) better place for underrepresented and disadvantaged people. If you don't, you are more precise and are making the world a (slightly) worse place for underrepresented and disadvantaged people.
What of these is more important?