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.
There are multiple great languages hiding within it
As proven a few times, it doesn't matter if committee decides to break something if compiler vendors aren't on board with what is being broken.
There is still this disconnection on how languages under ISO process work in the industry.
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.
And you will be the one telling the losers that their compiler, operating systems and OS doesn't count?
By the way this applies to the C language so beloved on this corner as well.
As it does to COBOL, Fortran, Ada and JS (ECMA is not much different from ISO).