I don't see how the large majority of security problems could be solved by any OS design. Human failures would just account for 95% of breaches instead of the current 85% (made up numbers). Not saying the OS improvements aren't useful nevertheless..
For example, phishing sites would be radically less effective if passwords are not a thing, and everyone logged in using hardware keys (e.g. Yubikeys) which cryptographically prevent phishing.
Of which there have been plenty.