Waffledynamics said:
Having kids is expensive/people don't make enough money to be financially stable, modern feminism has made dating difficult and made women hate men and commitment, and kids are socially stunted due to technology and Covid dysfunction.
You're close, but not quite there yet. It isn't a specific "wave" of feminism that crosses the cultural rubicon, it's the entire premise.
The premise of feminism is to free women from cultural constraints. Specifically in these crosshairs within the west was the complimentarianism of the Bible and God's ordered design. Feminism is inherently rebellion against God's order as can be seen with their fights for abortion, free-love, no-fault divorce, family headship, and bread-winning.
Poor people having more kids disqualifies the economic argument; it's a prioritization issue. Modern women have been systematically moved fed a propaganda of selfishness which has twisted them into consumers. The measure of "success" for a modern women is her ability to avoid domestic service for her family, which is the through-line in these otherwise seemingly contradictory outcomes.