First off, Google has made agressive deals with phone manufacturers to ship spyware with their phones by default, and some of the stuff can only get taken out by rooting/jailbreaking the phone. By doing so, they acquired nearly 100% of the app store market share, and then used it to make “useful features” such as integrity checks that are tied to the Play Services app (which is an always on spyware background app).
The end result is, even if you manage to root your phone and install a custom ROM (which is not always available to every model), a bunch of apps will refuse to work properly because you fail the Google Play fingerprinting steps and are assumed to be a security vulnerability. If I’m not mistaken there’s also some shady stuff with certificates, too

Google already does precisely that with their “open source” mobile OS. People underestimate how easily these guys can ruin stuff