In the early days, search engines were of dubious quality at best, and the only way to find really good sites was to just poke around and keep your eyes open and hope to stumble across them.
And it's really pretty much exactly the same today. Search engines are of dubious quality at best, since virtually all of the sites to which they might point us have been warped by money-grubbing corporate owners and/or buried under a flood of morons, assholes and bots, but once again, there are great sites and communities to be found if you just poke around and keep your eyes open.
It's almost as if the old internet has been recreated in little gaps and out-of-the-way corners of the new one.
The way that worked best would be to stumble across a site you liked with common interests and hope they had links to other sites of the same ilk, etc. The WEB! 🤪
Fediverse seemed to start out pretty strong, but little napoleons running their instances de-federate everything they don’t agree with, essentially killing the idea with their little walled gardens that would just be better off running phpbb or vbulletin.