I've pretty much just seen evidence that this segment keeps growing, and is now much MUCH larger than the Internet in The Good Old Days.
Discovering them is indeed hard, but it has always been hard - that's why search engines were such a gigantic improvement initially, they found more than the zero that most people had seen. But searches only ever skimmed the surface, and there's almost certainly no mechanical way to accurately identify the hidden gems - it's just straight chaos, there's a lot of good and bad and insane.
Find a small site or two, and explore their webring links, like The Good Old Days. They're still alive and healthy because it keeps getting easier to create and host them.
Sites today don't have blogrolls. Back in the '00s it was sacrilege not to have one on the sidebar of your site. That massively improved discoverability. Today you have to go to another service like Twitter to see this kind of cross-pollination.
tbh I have only ever seen a couple in an omnipresent sidebar in my lifetime. The vast majority I encountered around then and earlier were just in the "about" (or possibly "links") pages of people's websites, and occasionally a footer explicitly mentioning "webring".
Also if you squint hard enough, they're massively more common now. They're just usually hidden by adblockers because they're run by Disqus or Outbrain or similar (i.e. complete junk).
