I disagree. Technically, Android doesn't have a One True App Store. But in practice, Google Play is the standard app store and 99% of users use it exclusively,

I disagree. Technically, Android doesn't have a One True App Store. But in practice, Google Play is the standard app store and 99% of users use it exclusively, at least in the West. It is in fact the one true app store for Android. So Google does in fact control the Android app store (the one that counts, anyway). The reason why Google Play has so many shitty apps is because Google simply doesn't care about curation in the same way Apple does. That's true for every Google product, by the way. They strongly favor algorithmic curation, while Apple also relies heavily on human curation. If Apple allowed alternative app stores, nothing would change as far as the standard iOS app store is concerned. 99,99% of users would keep using the Apple app store unless there was a very compelling reason for using an alternative.