Why does everyone seem to forget the essential "have less kids" one ? This is what puts me into the defeatist group. As long as people won't even put their rep

Why does everyone seem to forget the essential "have less kids" one ? This is what puts me into the defeatist group. As long as people won't even put their reproductive urges in question (and rather discuss how flying is bad), how are we even supposed to achieve anything ? This should be one of the first logical moves, yet it's so frowned upon it's never brought up. Depressing.