The block feature only hides posts from those instances communities, not comments (unless you block individual users, but then you have to block a whole lot of users).
Also users from those instances will still have an influence on your feed via their voting. For example if you think an instance is a source of political propaganda, they can still promote that political agenda via voting.
Defederation is a more effective solution if you want to avoid an instance.
The block feature only hides posts from those instances communities, not comments (unless you block individual users, but then you have to block a whole lot of users).
Also users from those instances will still have an influence on your feed via their voting. For example if you think an instance is a source of political propaganda, they can still promote that political agenda via voting.
Defederation is a more effective solution if you want to avoid an instance.
The feed on my instance is only posts. I don’t browse comments unless I visit the post.