Just because a feature was not rolled out in the mid-90s would that mean that it’s not available today?
Adding a feature is one thing, C++ has added a lot of memory safety features over the years. The problem with C++ is it still allows a lot of unsafe ways of working with memory that previous projects used and people still use now. Removing support for these features will break existing code and piss a lot of people off in the process. It is not about adding new features, but removing the unsafe existing features that they are talking about here.
Rust mutexes would be nice. But I think for me that one thing for me would be its enums.