Maybe I've just missed it, but I have found pkg-config difficult to use and poorly documented. It's fine if you are installing things with a package manager, but I found it took some trail-and-error to figure out how to do this for my own lbraries, or for things built manually from source.

Also with c/c++ style system dependencies, I feel like there are a lot of issues with things like version conflicts which are solved much more simply by a package manager like cargo.

I agree that it's functional, but to say relatively easy I think is a bit of a stretch.