Everyone cares about speed first, or they would be using a more convenient slow language.

The challenge of Rust is, how nice can we make a language without noticeably giving up any performance to C++? Pretty nice, it turns out.

C++ still has an edge on both performance and ability to code powerful libraries that are not a PITA to use. The performance margin definitely will close up. The library margin could, too, but it will require unpleasant choices.

Anyway both are faster than almost anything else, and will stay that way, for von Neumann machines. Those might get less important, soon.