What Nix and build tools need to agree on is a specification or protocol for "building a software dependency tree". Like, I should be able to say 'builder = cargo' in a Nix derivation and Cargo should be able to pick up everything it needs from the build environment. Alas, there is simply far too much tied up in nixpkg's stdenv for this to be viable, so we have magic stdenv builder behavior via hooks when a build tool is included in nativeBuildInputs.
There's no real way to do that at a language level - we cannot have "Go has determined the package you are trying to fix has not met the versioning requirements proscribed so you cannot submit the patch to fix it"
What language dependencies do is what OSes would think of as "unofficial versioning" that is, an OS will let you install and run an unofficial version of some lib (we've all been there, right, multiple versions of some core library because one doesn't work with whatever you are trying to install), but they will not manage it at all.