> So much could be solved if you could just say "this version of this package" in a dependency

This can be done in the JS/TS world. It also occasionally breaks horribly in the JS/TS world. You might have multiple incompatible versions of a package in the tree when one dependency depends on one particular version, and the rest of your universe depends on another. It gets even worse when `Symbol`s come to play, since they'll be unique between those two versions.