My experience is mostly through consuming packages that other people have written, and the downloading existing packages is a big part of why it's problematic.

My experience is mostly through consuming packages that other people have written, and the downloading existing packages is a big part of why it's problematic. If I already have PrettyCommonStandardLibraryX, I don't really want Bazel to download another copy of it for me just to incorporate your project. Other build systems are simple enough to change, or support this straightforwardly. Doing it with Bazel is quite painful IMO.