One of my favorite areas on the Internet are the Totalfark forums. $5 a month is a great gatekeeper that keeps a lot of the reddit and 4chan edgelords out.
Payed entry skews the conversations to older, established, wealthy people, true. It also attracts people like me that are fed up with the public facing internet. The opposite side of the equation is a site like 4chan where the abrasive culture weeds out people. That model has the effect of skewing conversations to young, poor, college-aged, STEM students. At least the payed entry has the potential to not be an echo chamber, at least not as much of one.
One thing I wish Hubski did was not allow Google to index threads. The astronomy forum I am on blocks people from reading topics unless they are logged it. Once a month or so, someone will complain about that, and I'm glad the people running the site are digging their heels in. Nothing inside the site shows up in a google search. Pain in the ass if you are looking for an answer, a life saver if you are trying to have a conversation.