I think the idea that a new Mastodon user is supposed to pick an instance based on affinity/interest is the number one thing that prevents people from joining. I think there needs to be a retooling of the messaging to make it about trust.
People don't join email services because of affinity. They do because they trust. They trust Google will be around for a long time. Or that hushmail won't sell their data. Or that Hotmail is easy to use. Etc etc.
@aaronpk This I have wished for too. And just generally more centralized information about instances. Perhaps it's out there but as a newbee I've got no clue where to look.