> Maybe there needs to be a tiny (incomplete?) rust compiler. Or maybe there should be an interpreter.
In which case the issue is "Rust doesn't have a small compiler" or "Rust doesn't have an interpreter". Having multiple compilers won't necessarily mean that those issues are resolved. A more generic argument would be something like "the existing compiler doesn't cover my use cases".
That's the way it's resolved in languages with a standard, multiple compilers and no preference towards any of the compilers. This doesn't mean it has to be done this way in Rust.
It seems like Rust is leaning towards doing that like it's done in python. One reference implementation, a language reference and a bunch of design documents (PEP, RFC). There are some areas where the language reference is lacking right now but that can be, and is being, fixed over time.
Most people don't. But most development moved away from C/C++ before rust.
If you want to call C & C++ "deprecated" you can't ignore the margins, which is exactly where those languages thrive.
Maybe there needs to be a tiny (incomplete?) rust compiler. Or maybe there should be an interpreter.