Earlier quoted context omitted.
> How does literally every single other platform manage this? AFAIK none of Android, Windows, the many Unix-like OSs, even Apple's MacOs have such restrictions on browser apps. They don’t. All of those platforms are less secure than iOS.
> All of those platforms are less secure than iOS. Do you have a source for this statement, specifically in relation to browsers? Let's consider Android. I wouldn't automatically assume that using Safari on iOS is more (or less) secure than using Chrome or Firefox on Android - they are all provided by well known tech companies with years of expertise building browsers and a focus on security.
Controlling the execution environment is part of iOS’s defense in depth strategy. Focussing on browsers alone is a red herring. You have to look at the whole system.
It’s true that Google or Mozilla may be able to produce an equivalent level of security in a browser engine, but that’s a false comparison, since alternative browsers are not limited to just these companies.