Debian's popcon has by-category lists, so e.g. here are the most popular packages from the category "shells", sorted by most installed:

https://popcon.debian.org/main/shells/by_inst

This is such a great idea, I never knew I wanted this either (and now I do).

Would be a great bit of feedback for the Arch devs, or even a pull request.

One way to identify libs could be looking at the package contents list since libs would write predominantly to /usr/lib and /usr/include (ignore writes to /usr/share) and probably no writes to /usr/bin. Not perfect but could give you a vague idea how to differentiate between bins and libs.