I think I might setup future networks to block all incoming AND outgoing connections by default, and then only open the ones I know or want (and perhaps even some of them “for a time” when clicked).
I've had that same thought, but fairly quickly been overrun by the number of things that need rules defined that I've gone back to 'just ban known badness'. (even my pihole setup needed an exception added recently for the one-off usage of a streaming service for the missus).
I already block the IoT junk/cameras.