Let me be clear--I see Nostr as the savior of online communication . We (as its stewards) need to be EXTREMELY careful to not destroy it as it grows and matures.
Conceptually (IMHO) the answer is to create blacklists / whitelists that users subscribe to--those lists can be created by node operators or by external groups--and then the INDIVIDUAL chooses to enable those lists or not.
We all do this already--most here do not look at the "global" feed--but I would NEVER say "let's just turn off global--no one reads it". But that is exactly what you're advocating for.
Free and open communication is just that--and it's MY choice to decide what I will (and will not0 listen to. And it's NOT your choice to do that for me.