Protecting JIT-compiled code, e.g. within browsers, is at least as important a concern. Some would argue much more important, especially as usage of services like Cloudflare Workers increases.

Techniques like CHERI could replace MMUs in some environments, potentially improving performance.

There's no way to express an out of bounds memory read/write in JavaScript. So you don't actually need an MMU, or CHERI, or pointer signing, or any of the stack smashing mitigations put in place for C.

You do have to generate correct code but that's actually a solvable problem, web assembly did it.

In theory this could unlock tons of performance (and free up some silicon) if we could ever get the rest of the system away from C