As an instance admin, I would be all in favor of some sort of group blocklist I could subscribe and unsubscribe to. Maintained lists of things like csa, loli, or other things would be extremely helpful, and would encourage more people to run their own servers.
While I get that individuals want free and open and a choice, fact is is that they aren't the ones running these servers. It's admins who have to risk things to host for other users - and giving admins an easy safety net out of the gate would really help.
I've imagined something like an API through fediseer that my instance could hook into, then select specific lists that I want to block