It has been many years since I shipped a memory bug in C++. It is just not a real worry for me. I am constantly dealing with design, specification, and logic flaws, which affect Rust equally, or moreso.
I am aware that there are plenty of other programmers out there, writing bad code in what they would call C++. I would like them to write good code. If it takes Rust to make them write good code, so be it. But if they began writing decent C++ code, that is just as good.
The threshold is not zero memory errors. The threshold is many fewer memory errors than logic or design errors. The more attention your language steals from logic and design, the more of those errors you will have. Such errors have equally dire consequences as memory errors, and are overwhelmingly more common in competent programmers' code, in C++ and in Rust.
C++ is (still) quite a substantially more expressive language than Rust, which is to say it can capture a lot more semantics in a library. Every time I use a powerful, well-tested library instead of coding logic by hand because it can't be captured in a library, that is another place errors have no opportunity to creep in.
So it's great that Rust makes some errors harder to make, but that is no grounds for acting holier-than-thou. Rust programmers have simply chosen to have many more of the other kinds of errors, instead.
Every programmer who switches from C to Rust makes a better world; likewise Java to Rust, or C# to Rust, or Go to Rust. Or, any of those to C++.
Switching from C++ to Rust, or Rust to C++, is of overwhelmingly less consequence, but the balance is still in C++'s favor because C++ still supports more powerful libraries.
You might disagree, but it is far from obvious that you are correct.
