Blue Sky “fixed” that by only having one instance.
I suppose we could “fix” it in a similar way by inviting people to a specific instance instead of pointing them at join-lemmy.org.(Although that site has improved massively since the last time I saw it.)
Don’t even mention instances or federation, just say “hey you should join me on <favorite instance URL>”.
Once they are using it, that’s the first hurdle, and they’ll notice pretty quickly that there are other servers that all (mostly) talk to each other.
I don’t think they were intending to be snarky. At least, not towards you. Perhaps towards society brainwashing us all into thinking that generations are useful in any meaningful way.
If anything, they are encouraging you. Go find stuff you like, it doesn’t matter how old/young the other people who like it are. If you can’t find those communities, make one! That’s one of the beautiful things about Lemmy; it is what you make of it.