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!
(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.)
If you avoid building on something that's constantly shifting (the web) then the need to update goes down significantly.