I've used a lot of social networking systems over the years based on a lot of technologies. I deeply understand the nostalgia for blogs and RSS—I had a blog for many years and have used an RSS reader continuously since probably 2002. I still enjoy reading blogs to this day.

The problem with blogs, though, is that there is no great solution to limit the visibility to certain audiences. It really limits the types of things you can share. At least with Facebook, you can limit posts to your friends or groups of friends. But even that is not really practical—it's too much effort to have every person curate every other person they know into groups for access control (Remember "circles" on Google Plus? It didn't work).

I think the right model is to allow distributed communities to form organically and then use those communities for sharing permissions. By "distributed communities" I'm thinking of things like email lists, Discord servers, phpbb forums—communities where membership is symmetric and there is a shared sense of who is in the community. Blogs don't have anything like that.