SSB is a store and forward network, so this is sort of built in. Basically, you only see posts that are within a configurable number of hops in the follow graph, and if you block somebody then you don't replicate any of their posts to your followers, so if everybody you follow has somebody blocked then you'll never see their stuff even if they are followed by somebody one hop further out.
(Default hops is 3, and most people use 3, so functionally this doesn't matter much. But if it was 5 or something, this would matter a lot. It's also sort of why people recommend unfollowing pubs once you've built up a network you trust -- because pubs will connect to anybody who requests it, so even users with no redeeming qualities who no human being would choose to follow, like dedicate griefer accounts, will end up being replicated by a pub.)
(Default hops is 3, and most people use 3, so functionally this doesn't matter much. But if it was 5 or something, this would matter a lot. It's also sort of why people recommend unfollowing pubs once you've built up a network you trust -- because pubs will connect to anybody who requests it, so even users with no redeeming qualities who no human being would choose to follow, like dedicate griefer accounts, will end up being replicated by a pub.)