The Fediverse is huge and much more than Mastodon, but does not include Nostr or similar protocols. I use services, that are not Mastodon, but part of the Fediverse, myself (Lemmy, Pixelfed).
Blockchains and web3 are certainly interesting technologies, but caused a huge bubble and many scams in the past. This caused a lot of scepticism and is also the reason I don't believe in them. There may be good usecases for these technologies, but I currently don't see them.