I would argue (minor caveats) that StatiCompiler + StaticTools are “stable enough” for some things in production, see this thread. They will get even better over time, but they’re usable right now.
And answering the question, Rust/C++ and other languages have other sets of features and target objectives, like interfaces for Rust and C++, memory safety for Rust, and the case that both languages are more guided to systems programming. Those features do make them more useful for some task, so Julia will not replace them on what they do well. 