If people can’t understand what federation is then just send them directly to .world or lemm.ee or another big instance. If they have common sense then send them to join-lemmy and let them pick an instance. If someone is unable or unwilling to learn a very basic concept then they probably are not going to be a very good neighbor to have on the fediverse.

I agree that the discoverability of communities needs improvement. I think that most instances should add starter pack like features with the most popular communities for people to choose to subscribe to when onboarding new users.

In my opinion, finding the right and active communities to subscribe to is the biggest onboarding hurdle, not picking an instance. If picking an instance is a hurdle, that person wasn’t willing to try another site in the first place