The exceptions are: SMS, Settings, and the Phone app for the numbers tied to your SIMs (there’s still a billion VoIP options including extra lines from carriers like T-Mobile’s Digits) and probably a couple others I’m forgetting. I think the Clock app has a couple of privileges not available to 3rd parties actually.
You can use a 3rd party browser, but that browser will use the version of WebKit that comes with the operating system (except soon, in the EU, whenever 3rd party browsers with their own rendering engines ship there).
* no alternative browser engines
* no alternative wallet apps
* no alternative app stores (specifically so Apple can capture a % of sales)
* no software streaming
* no super apps
* Apple-only special SMS features
* Apple hardware (watches) get special access to iPhone hardware
that stuff adds up
So, something like WebUSB comes out? Gotta wait for Apple to implement it, and also for your customers to upgrade their devices.
On Android, I can install firefox-for-android and run ublock origin to no longer see ads on websites.
On iOS, that's not possible. Apple prevents mozilla from shipping a browser capable of running firefox addons.
This is a case where Apple's policies are hampering security since, well, blocking ads on the web is the thing has had the single largest positive impact on security for my elderly relatives. Giving them ublock origin stopped them from clicking on a ridiculous number of scammy ads and popups.
I also want alternate web tech, WebAssembly, Javascript implementations.
And as a developer, to be able to create tools that use the memory allocation/permissions API for JIT compilation.