I was also curious about issues like this. You can see that community from kbin here: https://kbin.social/m/[email protected] but also if you go to that page it says "The magazine from the federated server may be incomplete. Browse more on the original instance." And indeed, from kbin you can only see 4 posts and 15 subscribers, but from the lemmy.ml page you can see 109 posts and 377 subscribers. I'm not sure what the issue is. Best I can tell, kbin is just a fairly new service and things are still being figured out.

Why won't teenagers come here along with everyone else?

Yes, particularly for the more niche communities