I have to say, 98% of me being confronted with spam in the Fediverse is other people talking about it. This comes down to excellent moderation of my old main account. But what delights me even more is how quiet it is on my own private server, with no moderation at all.
Of course this is a really small account and everything, but if you don't enable open sign-ups and require to approve follow requests, a big part of the problem is covered.
I see people complaining -- and guess what? 9 out of 10 are on mastodon.social. I totally get that not everyone wants or is able to host their own server. That's fine. But if you're joining the Fediverse on mastodon.social, then complain that Mastodon or even the Fediverse is bad because of spam, without every trying another server, you kinda missed the point.