When fathers in Spain were given more parental leave, they have less kids, for example. The revealed preference is clear.
https://ourworldindata.org/grapher/children-per-woman-UN
https://qz.com/work/1614893/after-men-in-spain-got-paternity...
The study doesnt mention any effect on career progression or any other type of opportunity cost either. You’re entitled to your opinion but this article does not support it.
I'm reminded of societies in which families have more children than they want because there is no social safety net. Children are the safety net. Talk about harvesting human beings. Children suffer immense pressure and even abuse in such places.
Which will lead to a more stable society: social safety net, or no social safety net?
In my experience and observation, societies that have protections from poverty seem to be far more stable as compared to societies that do not have them.