I thought circles was the best idea. I loved having a bit more control over posts. Unfortunately, only two of my friends used it, so it was worthless for me for the most part.
It was a pretty cool platform but their biggest problem was making it invite only, therefore forcing it to be smaller than competing platforms. Invite only may work for Gmail but not for social media.
I don’t really know what is the problem with google+ except they are born in the wrong time where Facebook are still on the rise, instagram is new and trendy and Zuckerberg is not dreaming on metaverse
One of the things that probably killed it was Google enforcing people to use their real names on there. Which of course affected also commenting on YouTube as well.
I quite liked Google+ overall. Would have been good to have a proper competitor to Facebook.
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.