They won't let you call anything but their crappy camera app by intent already, for supposed privacy reasons. As you intimate, what is the point of allowing mobile apps, if they can't access any of the features of the device? Because that is where they are heading, fast. A few crappy google apps that require 24/7 spying to work, and then they "protect you" from everyone else. Sounds like an old school mafia street racket.
That sounds like iOS? Only Apple apps have access to all the system level capabilities and you can't replace any of the system apps, not even the browser.
It would be fair if one were to conclude that I don't like iOS. But my comment made a few different points, including about google's app quality, not only forcing default apps but also disallowing user choice where it should exist in a pervasive, hard to see way (for the end user), and invasive tracking.
Frankly, over the last week I have been looking into whether there is a relatively straightforward way to write an app for a mobile linux, because I am at the point I am willing to get rid of several common apps, such as banking apps, to get off this nauseating hamster wheel.
There is Anbox, which just uses the same kernel for Linux and Android. But it is incomplete and not very active. Basically, we don't even need a hypervisor, but apparently it's still not easy.