I think parent is saying to use a package manager.
Also, separation of concerns is a good thing IMO.
"Separation of concerns" is ill-defined — you can use cargo as just a package manager, just a build system, or both. Most people use it as both but there are definitely places (e.g. bigcos) that use just one of the aspects of cargo.
What is missing is a modern cross-language, cross-platform package manager, I agree. But there are really good reasons for that, chief among them being that I don't think it's possible to define the scope of such a thing in a coherent fashion.
Indeed, and I'm still highly skeptical. Learning Rust has been an amazingly rare sequence of "wow that's perfect" uttered from my mouth – except for Cargo. I couldn't disable the networking functionality of Cargo fast enough!