I don’t disagree with anything you’ve said, but just to the specific narrow example of UE’s ACharacter: there’s nothing stopping you using APawn as your “player” and composing the collision, mesh, movement and functionality as you please - in fact, I suspect the majority of people using Unreal Engine for anything other than toy projects would do just that. I think the “pre-composed” ACharacter exists mainly to help with quick prototyping.