I don't know, but I am just pointing out that the problems here are really about execution, not vision.
There's no reason we can't properly enforce security boundaries in the browser, we already do it between the website's code and the local machine.
These ideas have been around a long time and predate the internet. See for example Liskov's work on Thor:
https://dl.acm.org/doi/pdf/10.1145/233269.233346