I wouldn't even put it on poverty, because large population booms have happened under impoverished conditions elsewhere without issue.

But there's a huge social taboo against pregnancy at virtually any age. Children are treated like luxuries. They're enormously expensive to have and to raise, and everything about childhood is commodified to shit. Add to that how people are all terrified of one another. Men are told to put their prospective spouses on a pedestal, so they've all got to be supermodels with PhDs and rich parents. Women are inundated with the grossest men imaginable in dating markets that reward you for being an annoying creep. Everyone is told to hate one another constantly by a media apparatus that profits off your alienation.

We also seem to absolutely hate kids, in this modern moment. They're constantly presented as violent, parasitic, gross, vulgar monsters.

So much of this is just mass media bombarding us with bad advice and bigoted worldviews. How is anyone supposed to procreate under these conditions?