I closed registrations just over 2 weeks ago on infosec.exchange. In that time, I've had exactly 2 people ask me to register, only one of whom actually did. I suspect the convenience of the internet has trained people to just move on if the experience isn't frictionless...
Or there were just a lot of bots or lurkers before shutting off open registration. The infosec.exchange timeline is active, but pretty low volume based on the user numbers.
A Mastodon instance for info/cyber security-minded people.