Good point. Wicked also is an imperfect example because it was written for adults, unlike the examples in the grandparent.

I wonder if there's something different about the way (most) authors write books for children and (some) authors write books for adults - HP, Narnia, Star Wars, and Oz all had young audiences in mind. Most of the more morally complex movies mentioned in the grandparent were for adults. Do any of Stephen King's bestsellers have moral complexity?

I also wonder if those writing and creating works for children (if they do gravitate towards moral simplicity) have the correct understanding of what their audience wants? Of course, HP and Star Wars certainly broke out well beyond children, so maybe a lot of adults want moral simplicity too.