"All of the announced cast members but one are white."
Incorrect. Of the nine actors named for leading and supporting roles in this show, two are black. Of the other seven, five are playing members of the same family, for whatever that's worth.
"Are you really objecting to the observation that 'it isn't very diverse'?"
I'm questioning whether you think there is a certain percentage of actors of color that you would consider to be acceptably diverse in casting a show, and what that number might be, and whether you would break in down in terms of various races and nationalities (African Americans, Asians, Latinx, etc.)