Microkernel architecture doesn't magically eliminate bugs, it just replaces a subset of kernel panics with app crashes. Bugs will be there, they will keep impacting users, they will need to be fixed.

Rust would still help to eliminate those bugs.

I agree it doesn’t magically eliminate bugs, and I don’t think rearchitecting the existing Linux kernel would be a fruitful direction regardless. That said, OS services split out into apps with more limited access can still provide a meaningful security barrier in the event of a crash. As it stands, a full kernel-space RCE is game over for a Linux system.