I don't really think this is a problem anymore. It's more that no desktop OS provides secure native execution facilities a la iOS. The web browser was the best solution for sandboxing web applications in 1995-200x, but now CPUs have multiple cores, virtualization extensions, systems with multiple gigabytes of ram, etc.

There are better ways to sandbox applications in 2020.

As an interesting counterpoint, since iOS sideloading became semi-possible around 2014, there have been many more app-based Jailbreaks than Safari-based Jailbreaks.

This is true despite the fact that on iOS, sideloading custom apps without a developer account is extraordinarily inconvenient.

I'm so sorry to respond so late; I would just like to point out "the cloud," and the fact that there have been very few hypervisor escapes. Just because there are more app-based Jailbreaks on iOS has little to do with what is technically possible given the hardware (recent Intel missteps notwithstanding).

Personally, I'd rather live in a world where you could tell a web app from a document before you opened it. No need for apps to be native, but on a different protocol.