People who believe in total unsuitability would be acting silly indeed. But most would agree that writing code on languages that provide better and safer tooling is a positive.

Sure, the main Rust compiler currently depends on LLVM, which is currently written in C++. But the rustc team might choose to follow a similar path to Zig and replace LLVM, or LLVM might get rewritten in Rust.

Finally, while most bugs are logical, the most damaging ones, security bugs, are primarily related to undefined behavior.