No you are not alone in being shocked by that statement. What they could have more accurately said is that C++ is becoming a legacy language within the subset of programmers that contribute to wide open open source projects hosted on GitHub. This is an important factor to consider for a project like Fish, given that the viability of the project depends entirely on getting (quite often very young and very bought in to the latest hotness) programmers to contribute their free time.
Serious business obviously still writes in C++ more than rust and so it isn't legacy, but I can see why somebody may not be excited about spending their free time writing C++, and so Rust is the better choice if it gets people excited to contribute.
Serious business obviously still writes in C++ more than rust and so it isn't legacy, but I can see why somebody may not be excited about spending their free time writing C++, and so Rust is the better choice if it gets people excited to contribute.