Most of these already exist
Rings are code privilege levels, they don't "protect" memory, page tables do that, and the implementation to protect the stack has been around for over a decade - DEP
call/return stack detection is very new, afaik only current generation intel processors have it under the name CET (control-flow enforcement technology). This works by a processor-level "shadow stack," which is pushed to on calls and popped from on returns, and throws a fault if the actual stack is returning to a different location
Pointer encryption is available on ARM as PAC (pointer authentication). Afaik there's no equivalent on x86 processors.
Hardware mitigations are gaining more and more traction, so hopefully all of them will be available across all major architectures within the next decade or so.
EDIT: another huge mitigation that's starting to gain traction is process-level virtualization. Qubes is most known for it, but Windows has been building more support for it (currently only edge and office support it, under the name "Application Guard"). The idea is that if a malicious actor is able to exploit a program, they would also have to break out of the vm the app is in to gain access to the full system, which can be a much more difficult task.