You mean like in the vast majority of American films & television shows? And when we DO try and ‘go make your own films if you don’t like it!!’ as many white people are fond of saying, THIS happens.
Having a mostly black cast in a film or play is NOT racism. Making your own representation when the white people won’t give it to you is not oppressing ANYONE, nor is it taking away jobs from white actors, who can easily find work in other films. The same can not be said for the people of color in that movie.
Acting like having a mostly black cast and having a mostly white cast is the same thing is creating a false equivalency. Sadly we have mostly white casts so often that it doesn’t even create an outcry, unless one or more of our few POC characters was white washed. This situation is so obviously not the same that I can’t even do anything but laugh at the ignorance of it all.