With software can't you just hack this by selling a free "Epic Store app" and allowing all games and software to be purchased there.

If the "store" is now the app then how does Steam get their cut? Do they just disallow any product that has a "store" inside of it? What constitutes a "store"?

This is the hard question. Apple has already reduced subscription cut to 15% after 1 year, but do they deserve even that?

This isn't bad. There _should_ be able to be an Epic Store app which sells products without the Apple cut. Since Epic has done all of the work setting up the store and processing payments.

Steam gets their cut by developers listing their games there directly. Epic already has a store app and yet Valve still makes money because the steam store and ecosystem provide value that justifies the cost even when alternatives exist.

IMO what cut Apple deserves is the wrong question. A democratic society can in principle decide that the public would be better served if Apple had to allow alternative app stores, and enact legislation accordingly. Whether Apple deserves to establish itself as the sole gatekeeper and take a cut whenever they can manage isn't really a concern. I think using anthropomorphic language like "deserves" for a company isn't even conducive to thinking about this.

I'd ask this instead. Would it be beneficial for society as a whole if iOS had to allow alternative app stores?

Why should Apple be forced to include an app store on THEIR operating system? If they want to be the gatekeeper of all their software, it is on them as a private company to do so.

It is likely beneficial for society as a whole for iOS to allow alternative app stores, but that doesn't make it right for the government to force them to do so.

If the citizens of a particular country want to force Apple to allow alternative app stores, they can. It's their country. Apple can ignore their market if they don't like the rules.