Maybe stores should simply be uncoupled with mobile OS. Imagine a store, that has apps for various OS, run independently from the OS' vendor, Google, Apple, whoever. Then we wouldn't have all the issues with the vendors behaving like dictators about what can be on _their_ stores, because it is no longer their stores. Only question: How does it get financed and maintained, if not big tech is behind it?
That's what Steam is. It works on both Linux, Windows, and macOS, and it sells apps for all three platforms. Funding isn't a problem, as Valve takes a cut of sales. The whole thing is only possible though since the supported platforms are not locked down.
For this to work in any reasonable manor it should work more like package repos in Linux.
There is absolutely no point to any of the 3rd party app stores, if you cannot install your banking, travel or payment apps from them. Who cares about an EPIC app store, where games are ever so slightly cheaper, if you can't install the app for your government ID from that store?
There needs to be multiple store fronts, with the option of adding different package streams so that any store can carry any app. This is obviously going to be to confusing for the average person and will make the app stores unusable for most.
The whole idea of alternative app stores is idiotic, unless companies and governments aren't being forced to distribute their apps on all of them. Maybe you can have two app stores at the same time, but then I question what we actually gained. I don't want 3rd party app stores because Google and Apple are overcharging, I want them because I don't trust Google and I want to be able to use an Android phone while not giving Google ANY information at all. But I really don't care that Apple and Google are charging developers 30%, I really don't. I have only a few paid apps, and they where price just fine.
