The issue is simply, how do we incentivize people to have more kids? Some countries have figured out...you can use this thing called "government" to create the incentives to solve the problem. Mandatory leave for both new mothers and fathers, massive tax benefits, subsidized childcare, etc.

Countries who have done this, while still being market-based economies (capitalist), have been successful in increasing their birth rate to sustainable levels! Maybe we should try it?