Its really easy to make a custom rom but hard to do serious "real life" stuff; companies don't want to make it easy. To most regular users, if they cant download apps from the google play store, and they can't use venmo\cashapp, then the OS is dead in the water from day 1
> You can pay app developers to port their apps off of play services, you can pay developers to add support for your attestation keys.
microsoft literally tried this back in the day when android/ios was rising against windows mobile... spoiler: it didn't workan additional anecdote from my time then: they came to where i was working at the time and proposed funding a windows mobile version of our app (quite a large sum) but our supervisor finally said no, because the upkeep of now 3 apps would be too much for too few customers
you cant just throw money at devs and expect much unless you have the user base (potential market) to back it up
1. It doesn't require an entirely new app. You can ship the same apk on all platforms.
2. Most apps already don't have a hard dependency on play services.