[js8]

I think you're onto something, but I think capitalism is the cause. Especially looking back at former communist countries, and comparing them with today. They had higher birthrates despite opportunities being often gender equal (communist countries sometimes being more progressive than the West) and both parents working (although there probably was more leisure time). AFAICT every post-communist country had a birtrate drop after switch to capitalism, and it wasn't accompanied with the cultural change in gender roles or equality (these happen more gradually).

Capitalism sees human labor as a resource to be exploited, and that is a powerful incentive (especially to educated women) to avoid procreation and family life. You want to work on your career early, and young people make the best labor.