No one cares if they cast POC. They DO care if the all male Space Marine chapters suddenly become half female, AND those women are potato shaped danger hairs, AND all the men suddenly turn into buffoons that make lame passes at said womyn just so they can be "owned", AND there are more LGBTQRS relationships than hetero ones, AND a third of the cast are trans that DO NOTHING but talk about how they are trans, AND all the alien races are represented as aggrieved indigenous peoples oppressed by colonizer humans (that just happen to be the handful of white cishet dudes in the cast), AND there all sorts of socialist ideas and "orange man bad" TDS crap wedged in because Bezos has a beef with POTUS.
It's the cascade of things that lead to total destruction of the product, removing it from everything the actual fans want, and then those same fans get insulted and called derogatory names for DARING to not support the product, even though NO ONE ELSE does either.
Casting a muscular black man to play a Space Marine and a tough arabic lady as an inquisitor ain't the issue here and its a bit annoying to keep repeating that it is.