Some countries (the EU in general) are already doing things about this. Owning the app store means you are a monopoly and now the only question is are you illegal by the local laws which vary.
You can/should write your congressman (or whatever they are called in your country) and get better laws in place.
You are not wrong that regulation is desperately needed, and that EU is doing good things. However, even the EU which are doing the right thing on an anti-trust pro-competition basis, they fundamentally succumb to the same misconception – that middlemen are necessary at all. The EU doesn’t care about the App Store model, they care about the App Store monopoly. They are right about that, but the solution isn’t alternative app stores - it’s much simpler: the solution is NO App Store.
More specifically, it used to be feasible to distribute software between me (the developer) and my customers (the users) without a mandatory gate keeper that looks at me and decides whether I’m worthy, am from the right country, have good intentions etc. This is currently necessary on all desktop and mobile platforms except Linux. There is exactly 1 gatekeeper per platform (the platform owner who controls your device), except windows, which effectively have like 3-4 CAs that’s shrinking every year due to mergers and private equity ownership.
Software curation and reputation systems can be good, either with whitelists (say steam) or blacklists (say antivirus). I can see some use cases for it, but they should be within user control. What we have now is worse than a fearmongering Stallman rant. It’s incredibly bad, both pragmatically and philosophically.
If arbitrary app stores are allowed without restrictions, isn't that equivalent to allowing installation of any apps?