Yeah. Lemmy and Reddit are basically mega-forums. The voting and threading systems went a huge way toward solving the problems that made traditional forums unworkable at large scale. e.g. there were always 8 pages of replies to trudge through to find one relevant answer. (XDA is a great modern example of this problem. Woe to those who find an XDA thread while troubleshooting.)
It was also so, so much easier for someone to make a subreddit than host and maintain their own phpBB server. I am speaking from experience on both ends, there.
Reddit killed the traditional forum, and you know what? Good. It was time.
The same problem makes large Discord painful to use.