Couldn't people move over to another app store like F-Droid?

As far as I know:

Most app available on Amazon's app store are already available via Google Play Store anyways. Rather, most developers have deserted the Amazon's store and the versions available there are outdated by years. I noted that Apps Amazon released for their own external or internal events like AWS re:Invent were only available via Google's Play Store and not Amazon's own.

The challenge is that many apps on Amazon's app store are tied to the app store. I once tried disabling Amazon's app store app, and noted that the apps installed stopped working (until the app store was enabled again). My immediate conclusion was that I would not want to rely on these apps or Amazon's app store. The developers may not have any incentive to update their apps versions on Amazon's store to remove the dependence on the latter, and nor they may have any to allow the paid users just install those apps from Google's play store without paying afresh.

F-Droid only accept opensource app.