They're shutting it down precisely because no one was depending on it. How would anyone depend on a social network without any users?
Them: "We're shutting down X because too few people use it. Also, announcing Y!"
Users: "I'm not using Y. You'll probably shut it down."
[months pass]
Them: "We're shutting down Y because too few people use it."
It did have users. I have no idea the exact number, and clearly it wasn't as many as Facebook, but it wasn't the ghost town people always made it out to be. Some of the Communities were actually quite active.
> "The consumer version of Google+ currently has low usage and engagement: 90% of Google+ user sessions are less than five seconds."
While i'm sure power law applies, 5 seconds is a hilariously low amount of engagement for the 90%
Their only advantage to Facebook groups was more natural (temporal, not recommended) sorting of data.
Some Linux kernel devs IIRC (I do not hang there).
Some local people.
One user I followed who was very into clean energy solutions.
Gardening (vegetables, chilies, general).
Ham radio.
The thing I never saw on Google+ was politics (I guess it is there but I never looked for it and never found it : )