You overlooked what I consider to be the first thing you should check — when was the repository last committed to. There are countless projects that rank high on every other metric, but are essentially abandonware.
Yeah good point... definitely something I would have checked, forgot to put it in the list. I'm baffled people have trouble coming up with more than "number of stars" for this.
Of course there can be libraries that are more or less "finished", so the last commit/frequency of commits isn't on its own a deciding factor, but in proper context/holistically it is definitely an important metric!
FWIW, I am not baffled by that, as the vast majority of programmers are not "talented professionals" (which is the specific category of potential employee I was balling at, along with enterprises and venture capital firms). So like, you ask your question, they say "star count", and you don't have to really continue the interview.
(When I was in high school, I used to work for a pre-Internet company that helped people pre-filter interview candidates for ads posted in classified sections of newspapers and what they did was have questions like this that could be asked by people well before they reached your calendar for an interview.)
However, some language ecosystems are more OK with "finished" software than others. It hasn't had a commit in 4 years because none were necessary. Needing constant updates is a sign the local ecosystem is driven by churn over quality.
I don't really think this generalization holds. TeX is one of the very few widely used pieces of software that's considered complete, more or less everything else is either getting updated or superseded by other things.
Clojure, Elixir, and Lisp (especially Clojure) all have slower acceptable churn rates than other language ecosystems. If it works sensibly (both in terms of being fully debugged and ergonomics) and the underlying system hasn't had significant changes, what good does a commit within the past six months do beyond signaling to the GitHub meta game?
