"Drivers are exploitable so we should run them in userspace" is a hack, and not a good one.
The problem is that drivers are exploitable in the first place, so the solution is that we should make them not exploitable (using Rust, or a better language than Rust that fixes some of its problems) and try to preserve our performance that is rapidly being stolen away by bloated userspace software, rather than just shrug our shoulders and say "oh well, I guess that drivers are just intrinsically insecure".
The problem is that drivers are exploitable in the first place, so the solution is that we should make them not exploitable (using Rust, or a better language than Rust that fixes some of its problems) and try to preserve our performance that is rapidly being stolen away by bloated userspace software, rather than just shrug our shoulders and say "oh well, I guess that drivers are just intrinsically insecure".