A modern security and privacy conscious OS would be "principle of least privilege" from the ground up. It would be written into the DNA of the kernel and OS from the first line of code, not bolted on later via permission managers and leaky APIs and then mandatory notarization by a central authority to work around the fact that the whole mess is still insecure.
We do have something like that. It's called a web browser. A browser is a small VM that runs utterly untrusted code relatively safely. In many cases it's code from the sketchiest ad networks and other hellholes imaginable.
Imagine if your real OS were like that. Install anything even known malware with fairly strong confidence that you're safe and that it can't do anything you don't explicitly grant to it.
> We do have something like that. It's called a web browser. A browser is a small VM that runs utterly untrusted code relatively safely. In many cases it's code from the sketchiest ad networks and other hellholes imaginable.
Given how many issues there are with ad tracking, fingerprinting, and other privacy related issues, I don't feel the web browser is particularly safer than an iOS app. What can an iOS app really do that a browser app cannot at this point?
[1] https://blog.codinghorror.com/the-dancing-bunnies-problem/