That wiki page is a little outdated. The pinned thread is a little more recent but still missing a lot of offshoots like TheMotte.org.

Ironically the only off-site that ever really took off is the snuff film site which has 2.3M users now.

It's even worse. Many subreddits were taken over by bad actors. When they saw a popular community, they found at what times the mods were inactive (e.g. late night or weekends) and posted evil stuff. Then went to cry to the admins about the evil stuff staying up for hours and got their friends to become mods of the community. In the case of reddit, many people suspect the admins and 3 letter agencies were in the know, or at least played along to their advantage.

And if you self-host to avoid the risk of handing over your community to those sites under control, you get flooded with DDoS and hacking attacks (including state-sponsored actors). Sad times.