There have been a dozen CVEs reported against all of coreutils in the past twenty years. The most recent audit of uutils-coreutils turned up forty-four CVEs.
By all appearances they’re replacing battle-tested and fundamental tooling which hasn’t been a problem with extremely amateurish Rust. The threading highlighted in the linked post above seems pretty egregious.
Also for Rust based rewrites, they could start by bootstraping Rust compiler itself, dependent on C++ to start it.
They don't do it, because even though LLVM and GCC are written in C++, a pure Rust compiler would not scale to the same level of contributions, and existing capabilities.
I would appreciate Go much more otherwise.