They could use the heuristics to build a list of domains to block and then have someone review it. After doing it for a long time, they could build a neural mod

They could use the heuristics to build a list of domains to block and then have someone review it. After doing it for a long time, they could build a neural model on top of that, and automate it. As I have said, the reason they don't do it is not because they don't have the skills and know-how.