While acknowledging that most users are not a developer?
Compare it with computer (desktop/laptop) market. Users can install any software they found in internet that they trust it is safe.
> While acknowledging that most users are not a developer?
You don't have to be "a developer" to install, for instance, the sort of retro-gaming emulator you use to play classic console games. You just need a free developer account Apple ID.
> Through an app called AltStore, you can install emulators onto your phone through a method called sideloading. If you're unfamiliar with the term, sideloading is installing software without using the App Store.
This is not at all comparable to proper sideloading/allowing third party access. For starters, unless you pay Apple 100 bucks a year for a developer certificate, you're going to need to renew the application every week and you're capped to 3 applications at most. AltStore does some fancy stuff (by which I mean that you need to run a separate application on your PC which can handle the renewal requests - that's what AltServer is) to minimize the difficulty of this as much as possible, but that's still the rules Apple works with.
Secondly, Apple severely limits the capabilities of sideloaded applications - those emulators for example aren't allowed to make use of JIT, or Just-In-Time compilation, which is extremely important for decent emulation. This is also the main reason nobody has even tried to bring over a non-Safari browser using this method - you practically need it to have a browser that's decently usable.
It's practically useless outside of development purposes. AltStore is a pile of (very impressive) hacks to get around a system that's crippled by design.
Compare and contrast to Android, where the only difference between the Play Store and a regular application is that the Play Store doesn't get the regular installation window (something which is set to change in the next version of Android, so that alternate stores can also request this permission).
Either way - this doesn't matter. The Digital Services Act has already been passed in the EU, and Apple is going to have to offer third parties proper access to iOS without being allowed to gatekeep the App Store.
OK, but the usual counter-argument against the claim that there is genuine security benefit in the current situation, is that “nobody will use it”, “hide it several levels deep in settings”, or whatever.