I do not think package management should be done at the level of programming languages.

Strictly speaking, Cargo isn't part of the Rust programming language itself. Cargo is a layer on top of Rust, and you can use the Rust compiler completely independently of Cargo. I think bazel, for example, can compile and handle dependencies without Cargo.

I agree, it should be done at the project level - that is, if you care about portability, reproducibility, deployment, etc.