Knowing little about cpp modules and nothing about Gabriel Dos Reis, I expect a more design-by-committee type explanation for the result: the module system was probably a victim of having to be backwards compatible, abi stable, idiomatic, zero cost abstraction, be compatible with all weird cpp features, not hurt compile time, etc etc etc

I don't think its fair to attribute it to lack of skills or bad intent, unless there's some proof to any of it.

Yep I agree C++ lacks many features Rust has solid support for. But the real issue with C++ is the development process, almost all the people involved in the Module system are rather old and worked for Microsoft once. They are just in their own bubble and not having an open RFC-process blocks experts in that field.