One of its plus points (no pun intended) was that it was the first social media platform to allow more granular control over who saw your posts. You could people to ‘circles’ and limit posts to which ever circles of friends you selected (if I’m remembering this correctly).
I think at that time on Facebook, you only had the option of Public, Friends or Private. It spurred Facebook on to introduce more granular control as well. So if nothing else, Google+ was good for that.