Mindshare death is a very large overstatement given the massive amount of legacy C++ out there that will be maintained by poor souls for year to come. But you are right, there used to be a great language hiding within C++ if the committee ever dared to break backwards compat. But even if they did it now it would be too late and they'd just end up with a worse Rust or Zig.
The biggest problem with C++ is that while everyone agrees there is a great language hiding in it, everyone also has a remarkably different idea of what that great language actually is.
I don't agree there's a great language hiding in C++. My high level objections would be that the type system is garbage and the syntax is terrible, so you'd need a different type system and syntax and that's nothing close to C++ after the changes.
After many years of insisting that "dialects" of C++ are a terrible idea, despite the reality that most C++ users have a specific dialect they use - Bjarne Stroustrup has endorsed essentially the same thing but as "profiles" to address safety issues. So for people who think there is a "great language" in there perhaps in C++ 29 or C++ 32 you will be able to find out for yourselves that you're wrong.
The C++ standards committee’s antiquated reliance on compiler “vendors” holds it back. They should adopt maintenance of clang and bless it as the reference compiler.