It existed and still exists though, it's just that there is less incentive to produce this kind of content and leave it open. It's a natural result of how the system changes as people learn to game it and find ways to gain power or make it profitable.
There are modern websites that still bring those feelings to me. For example, this blog has impressed me with its content and creative visualizations: https://ciechanow.ski/ Personal websites and web forums just don't surface anymore when searching the web or browsing large communities/aggregators, but I can find them on places such as https://curlie.org/ (A modern-day web directory) and https://search.marginalia.nu/ (a search engine that focus on non-commercial websites).
Could you speak more about how your experience with Lemmy has brought back those feelings? I remember the sense of wonder I felt when browsing the web in the early '00s, when every personal website, php board and irc community was unique and discovering a new website/community was really exciting. I still feel this sense of wonder when I visit content-rich websites from that era, such as amasci.com, https://atlas.limsi.fr/ and https://sciencemadness.org/talk/.
What I've seen from Lemmy brings me back to the early years of Reddit, but I'm yet to find anything that really brings back the way I felt when I started browsing the web. But maybe I just haven't explored enough?