Bazel does a lot more than just download packages though. It can also track dependencies down to individual file level and isolate build steps to assure they don’t have side effects. This is largely why it is so big and need to be language aware. Add remote build cache and lots of other stuff.

A general package manager that only sees packages as directory blobs would not need to be that complicated. In fact I don’t think npm has this deep knowledge about JavaScript either, it just put stuff inside node_modules and calls it a day.

That said, it would be great if more projects adopted Bazel, its biggest problem today is adoption, forcing you to convert any dependencies to make it Bazel compatible.