I wish new C++ standards would make old c++ not work: old code could still be compiled with old compilers, and it would encourage developers to fix their code or rewrite it.
C++ needs it's python2to3 moment.
Cpp2/cppfront feels a bit like that.
I don't mean to say that c++11 to 20 are bad, but they are probably expensive and fastidious to implement.
No one needs a python 2 to 3 moment. It was not a moment, it was a painful decade or so.
There might be a better way to handle changes in C++, but being like Python is not a good way to go.
As for deprecating old C++, yes, I can see the appeal, but no, the community hasn't gone that route. C++ has always been a 'mix and match' approach, with different parts of the community using more or less of the language features, with the intention being that you can choose what to adopt when, and move older code bases forward (or not!) depending on individual concerns.
It's one of the C++ strengths, although it doesn't always feel like it.