Lemmy, or indeed the entire Fediverse, is middle aged nerds. Older non-nerds are on Facebook and Twitter. Older nerds are on IRC and Newsgroups, middle aged non-nerds are on Reddit, middle-aged nerds are on Lemmy/Kbin/Mastodon, younger non-nerds are on Tiktok and Instagram. There are no young nerds (see the growing epidemic of Gen-Z being baffled by Technology futurism.com/gen-z-baffled-basic-technology).
Social Media is like a school dance in the 90s. Islands of people will emerge with similar age and interests, and they just stay there, because that’s where their people are.