I don't have Google Services installed, and rely entirely on F-Droid, with no extra repositories enabled. I feel my personal information is much less likely to leave my device installing any app through F-Droid compared to any app on Apple's store. Despite how locked down the App store is, I still trust it less than a third-party store.
I believe Apple users end up with all the downside (limits on which apps can be built and easily distributed) and none of the upside (an app store with which I trust every single application on).
The ecosystem could support couple more app stores at most.
Any friction makes it easier for their competitors. I think the only app that succeeded with a 3rd party (Android) store is Fortnite, and their userbase is young and grew up with technology.
You can bet your ass that some entity you need to work with will be using this app store to push software onto your device that you don't want to be there. It could be your bank suctioning up your data to minimise their exposure to fraud. It could be your health insurer to check that you're not doing dangerous things like speeding, or living a sedentary lifestyle. It could be your own government making sure you don't seek out abortion information. None of this stuff is possible under the current app store paradigm. (We already got a taste of it when Facebook and Google were both exploiting Enterprise Certificates to bypass protections: allowing them to vacuum up personal information, social media/IM conversations and constantly track the user.
I have no idea how the regulation is planning on managing permission bits, the whole point of having the approval system is that a developer had to prove they needed access to your contacts, location, camera, files, etc. Why does a flashlight app need access to your contacts?
Meanwhile you'll constantly hear people reply to these talking points about the seldom app that slipped through the app approval process:
1. This doesn't prove that we don't need an approval process
2. The amount of malware on iOS in comparison to Android, Windows and even macOS is extraordinarily low, not just as a % of users, but in absolute terms. It's very difficult to argue that the app store approach is ineffective and only there to make money when the statistics prove otherwise.
tl,dr: There is an absolute shit show up ahead and people are too busy high-5'ing each other because they think they nailed it to Apple.
I'll probably end up having a NixOS phone down the line as that develops more.