Do you know what also happened to Japan in the early 90s? The crash of the 80s bubble economy, and the resulting almost 40 years of stagflation.
When people have uncertain futures many will opt to not have children, or just one child.
Changing up society to not require both parents working which then complicates childcare would cause a major shit.
But expectations also have to change, you can't be leveraged out the wazoo and busy running little Timmy to sports ball 1, and then sports ball 2, then art class, swimming, etc. Having your children enrolled in multiple activities and never having free time instead of growing up and exploring with their peers is having issues with social skills, and less community engagement.