If only relevant content is shared within a 'circle', people appreciate it, sometimes ignore it, and move on. Consistent controversy and drama is avoided, which just so happens to be a key driver of social media engagement.
IRC is too technical for many people I know, but they are willing to use, or are already using Discord.
In many ways, the problem with Social Networks isn't algorithms or whatever, it's the scale, and being on a small server with at most 50-100 other people is an incredible experience. I've met so many interesting people from around the world who wouldn't have the technical skills to navigate the IRC world, and I didn't have to blow up my brain in the process.
The difference between open and closed is meaningless for the cloud. Give me the raw storage used by any piece of software and I can knock out a script that will serve it. Give me any open source network and without the data you have a ghost town no one will use.