I would much rather switch to a compiler-restricted memory safe unmanaged alternative such as Rust, before I throw out performance for safety completely.

A lot of applications, such as video games, don't require the type of security others do, but require performance to a much higher degree.

Rust is a good middle-ground, since it does have some compile-time issues at the moment still which are getting better. But it is incredibly stingy about anything unsafe. Even unsafe blocks of code are borrow-checked.

Considering how slowly things run these days on any OS, and OS's specifically having performance issues, I doubt the user experience will benefit from a completely managed OS either, but I'm no expert.