I encounter this sentiment fairly often. The use case seems to be approximately "I want to browse all for discoverability, but I don't want to maintain an extensive blocklist myself," which seems somewhat analogous to me to the use case we see for shared blocklists between fedi instances we see between admins of fedi instances. Piefed has a mechanism for building and sharing such a custom feed, so if we had a feature to block communities based on custom feeds, users could maintain custom feeds, like my Seattle feed, and then people who are interested in avoiding Seattle content can block my feed. I think it could be implemented similarly to following a custom feed such that if new Seattle communities appear and I can add them to my custom feed, then it would be blocked for users who block that custom feed without needing to update their own blocklists. They might could even be composable -- perhaps if I had a blocklist for each neighborhood in my city, maybe I could be able to compose them as part of the city custom feed. The existing set of topics would meet the needs of the user in the linked comment -- they could block the topic "Non-American Football (Soccer)" and avoid all soccer content, or "Sports" to avoid all sports content.

I like how this builds on the top of existing functionality and puts a new spin on it. Great idea and not hard to implement either.