All of the major device manufacturers fork Android so they could easily block that and make it impossible to uninstall certain apps. Google could potentially force it in the licensing terms, but that might run into antitrust concerns.

All applications should be removable and all notifications should be disableable. Even Windows 10, which comes with all sorts of useless irritants, lets you do this.

Imagine how many people would accidentally uninstall the play store. Also, as near as I can tell, there is no actual legitimate "Phone" app available there.

They could have a functionality like the 5 tap thing to enable developer mode. The lack of an official Phone app is irrelevant since you could just download another one, assuming you want to be reachable via phonecall.