Public Opt-in blocked lists are probably the best approach right now. We could do that at a relay level but then someone else is deciding for you. At least with public blocked list you opt-in yourself, or for you child.

Then who maintains those blocked lists?

Satoshi solved this through verifiable consensus and most proof of work efforts.

Not sure we would ever come to a consensus on a blocked list, let alone multiple blocked lists (issue 0 blocked list, issue 1 blocked list, etc…).

Its up to the individual, at scale, to sensor themselves and children. That what freedom tech allows.