Imagine you are big on some niche community which exists on Reddit (let’s say, e.g, /r/civ)
You want to leave Reddit, you hear about Lemmy.
You sign up.
You go to browse.feddit.de and look for Civilization communities.
You find !civ and !civ, both of which with no activity in the last 3 months, and most posts are more about people trying to figure out what to talk about instead of actually talking about the thing that the community is supposed to be about. Not only this is confusing (do you need to have any relationship to either lemmy.ca and lemm.ee to join? Why are there two separate communities? If these communities are dead, should I create yet-another one?) but don’t you think that the most common reaction would be simply to drop the whole effort and just go back to browsing Reddit?
Now, contrast this with the scenario where fediverser.network has compiled a comprehensive map of all these niche subreddits and can point to at least one lemmy community, and also where the mirroring is using these bots to post relevant content to all of these communities.
Now you can sign up to any instance, and you check what would be the recommended community to replace your favorite subs. You go and !civ (yeah, I just created it). If the alien.top bots were running, the community would already have at least the 14 posts that were created on Reddit today and made to their front page.
And if you decide to join Lemmy by using alien.top itself, all of that could be made automatically. If you had 50 subreddits, you would be automatically subscribed to all the relevant 50 Lemmy communities, you wouldn’t even need to worry about having to figure out which-subreddits-map-to-which-lemmy-communities and your feed would be customized.
I don’t know about you, but to me the second case seems like a much better onboarding experience and I’d be a lot more likely to stick around if that was a reality.