Honestly, from all the Gen Z and younger kids I know in my life the big thing that's probably killing the fediverse is it's not a media-first platform.
Not a one of them really participates in text-primary social media, which is what Lemmy definitely is.
Mastodon supports it better, but there's so much gatekeeping around the "right way" to share media content that the few people I know that tried to use it just bounced off it because they couldn't figure out the technical and social aspects of how to interact, because it's just piles of conflicting opinions.
They will, however, spend an insane amount of time on TikTok or Youtube or Twitch or Instagram or Snapchat endlessly watching whatever comes up and scrolling along to the next thing or sending pictures/videos of whatever they're doing at that moment to their friends.