I like how we always talk about "core mastodon" or "mastodon" to refer to mastodon.social and a few of the safe space instances, that are all under 1k users.
The majority of the mastodon instances are actually more into tech than anything else and don't have any unjustified block lists (blocking illegal content only) like mastodon.xyz, mamot.fr etc... I think they're instances with the most active userbases too, though the bigger instances are the japanese ones, who really don't give a shit about politics.