I as a user can go to a community I do not subscribe to and block it. I’m not sure if that’s exactly what you are meaning. Either way I find that this is the appropriate measure for anything from spammy/annoying communities to ones that are just toxic. I think we should all be more concerned with curating our experience to what is useful to us instead of worrying about what others can see. Otherwise we begin the creep back towards centralization - which is great until it isn’t.
I hate to see that people are so disturbed at what others are doing on another community@instance that simply blocking it on their account isn’t enough. Nonsensical. And the logical conclusion is producing nothing more than a Reddit clone with many of the same weaknesses.