regarding mastodon, federations, and decentralized software
noble intentions, flawed execution. smarter people than me have talked about this and if you're interested you could start by reading tedunangst's blog post on the topic. he tried implementing mastodon's protocol ActivityPub from scratch and realized it's a mess.
others have tried cooking up alternatives like nostr which unfortunately has another possible problem: it's being developed / funded / used mostly by crypto bros. which doesn't say anything by itself but could be a warning sign. still i look forward to it and wish them the best.