That's a completely different point than the one you made originally. If you want to avoid being misunderstood, then make the point you actually intend - "a C++ replacement must function as C++ does" instead of the one you claim - "understanding C++ is the first step in replacing C++"
How do you propose "must function as C++ does" happens if not through understading C++'s uses?
As I said, it can also be done unintentionally (you create a new language without studing how C++ is used, and it gets adoption in place of C++), but this is far less likely and quite random.
If one really wants to create a replacement for a language, he should very much study the language he wants to replace, and find what he needs to provide in his new language and what he can improve.
The thing you added that, "no, he can just create a replacement" (without needing to study the previous language), might very well be possible in theory but it's very much improbable.
If you want adoption from C++ users and from projects C++ is used and for the kinds of stuff C++ excels, you pragmatically need to study C++ and how it's used, period. That was the case for Rust, for D, for Java and C# earlier, and of course C++ (who studies C with that intent). That was also not the case for Go, and that's one reason why Go (by Pike's own admission) failed to gain traction from C++ users.
Of course success is not guaranteed, but merely making a "superior language" is not a way to get C++ users off C++ (or any other language).
For the vast majority of people, a car functions as a horse used to before there were cars -- it functions better, in fact. Yet car designers are not required to be intimately familiar with horse care.
You are pointing out marketing issues. I agree that if you don't actually have a better C++ than C++, then you will have difficulty convincing most C++ users that they should switch.
By the same token, if you actually do have a better C++ than C++, it will be evident in the adoption of the technology.
Also at this point, if Java, Go, Objective-C, D, and C# have not convinced the current user base of C++ to use other things, then perhaps it is no more possible or necessary to convince these remaining users to switch than it is to convince modern horse riders that they shouldn't bother to ride, own, or breed horses. For them there cannot be a "better C++ than C++."
