Honestly, most package managers just bring their own problems. I'd rather commit source code than troubleshoot npm, pip, nix, maven, etc errors all day long. The only package manager I've found that works reliably has been Cargo (Rust).

I believe the current intended use is a human-editable "manifest file" where you specify desires/intent, preferably semver, ideally only as necessary, and a machine-generated "lock file" which specifies the actual hash of every transitive dependency, so builds are fully specified and reproducible.

But they all have to vendor as well if they want reliable builds. Otherwise you end up with everything breaking when a developer decides to do a forced push or take his repo off github.