compared to Nostr, the Fediverse basically doesn't have spam. bots? yes, but the bots on Nostr are on every free relay out there and they're posting junk in Chinese, and they produce more traffic there than the real humans do. quite a lot of the first-time setup for a Nostr user involved figuring out how to filter that out and to be heard above the noise.
Discussion
and so far, the simplest way to avoid spam is to follow paid relays only. some clients and relays also do filtering based on your social graph, which is also effective.