Agreed, hopefully this is addressed in a future update. And not just ticking boxes either, like, properly done, and not just for diversity reasons, but for realism as well. (ie Not any of that, "Well, there's your black zombie! Why are y'all still complaining? *Proceeds to add another 50 white zombies*)
Also, not all of the zombies are sexualized. Weak, unfortunately, but not all are put in there for lewd reasons. The Screamer comes to mind as you already pointed out, as well as Big Mama, Darlene, Arlene, the lab coat zombie, probably others. (I've been sleeping on and off tonight so I'm surprised I remembered that many.)