Structure society and economy in a way that makes it appealing to have children (both in that the hypothetical parents feel safe in doing so without endangering their own quality of life, and in that they can imagine the hypothetical children to be happy too), and people will have them.
People that think it’s purely an economic problem are wrong. Economic and political solutions are not enough. You also need social solutions too. Like make it cool to have kids and solutions that allowa women of child bearing age to be around other women who have young children
Having children in modern society is pretty isolating. We had it very good because our neighbors have children of similar age and we could share the burdens of cooking and watching them while simultaneously also seeing other adults. If both parents work and you do all your chores you have approximately zero time to socialize outside your immediate vicinity. It takes a village but nobody has a village any longer
Structure society and economy in a way that makes it appealing to have children (both in that the hypothetical parents feel safe in doing so without endangering their own quality of life, and in that they can imagine the hypothetical children to be happy too), and people will have them.