I think the issue regarding declining birth rates is far more complex than can be addressed in short article.

Combine that with society's need to optimize every available person of working age to participate in the workforce to compensate for the increasing percentage of the population that is too young to work or to old and you have a real problem.

Lastly, you have the huge cost associated with retirees making up an increasing percentage of the population.

All of this calls for a restructuring of society back to the extended family living under "one roof".

Retired grandparents can play a role in caring for their grandchildren especially if housing is redesigned to provide separate but attached living quarters.

There may even emerge a future where elderly couples without children and young families without grandparents "adopt" one another.

Bottom line, our society has trended toward independent living for the last 100 years, but perhaps that model simply does not work anymore. Biologically, humans live as long as they do, because the elderly served a purpose. They would raise the children, while the men hunted for food and the women raised food and maintained the household. We evolved beyond that model, but we may have "thrown out the baby with the bathwater".

The new model may be the old model redesigned. The elderly will be responsible for raising their grandchildren, while both parents work. Society provides some support services for when the grandparents are sick or disabled or perhaps when they need a "vacation".

I think this will still limit family size, but at least it would promote families.