"and that's not something they can or should do."
Why not? They provide a lot of other policing work, like use of wrong APIs, style violations, rejecting your app because there are already enough apps of that kind and you added nothing new, and all kinds of things way more fiddly than wholesale copying. They're taking a nice cut, they ought to be bringing the customer and developers some value for it. Isn't that the whole Apple Store value proposition?