Social media as a vessel for diverse discussion is a tall order. It’s too public, too tied to context, and ultimately a no-win game. No matter how carefully you present yourself, you’ll end up being the “bad guy” to someone. The moment a discussion touches even lightly on controversy, healthy dialogue becomes nearly impossible. Think of it this way: you’re hosting a party, and an uninvited stranger kicks the door ope…
They were not like group chats or subreddits, the circles were just for you, it was just an easy way to determine which of your followers would see one of your posts.
This kind of interaction was common in early Facebook and Twitter too, where only your friends or followers saw what you posted, often just whitelisted ones. It was not all public all the time. Google+ just made that a bit more granular.
I suppose that these dynamics have been overtaken by messaging apps, but it's not really the same thing. It's too direct, too real-time and all messages mixed-in, I like the more async and distributed nature of posts with comments.
Granted, if you really want a diverse discussion and to talk with everyone in the world at once, indeed that's a different problem and probably fundamentally impossible to make non-toxic, people are people.