You need to creative an economic incentive to have children. And I don't mean "mandate a few more months of paid maternity leave", none of that bandaid shit comes close to making kids an attractive financial decision for a 20-something. This isn't a cultural problem, and if it is, there's still an economic reality at its root.
Take the archetype of Shaniqua the food stamp queen for example - is she a based and redpilled trad wife? No. So why does she have 7 kids? Because in her position it makes economic sense - she has low standards for living, zero desire to work and gets free shit from the government for each new baby. Now, how do you make children an appealing investment to the mid 20s-30s professional working class who are currently making 1 autistic kid a few months before hitting infertility, if they're lucky? There isn't an easy to answer to this. Even simply banning women from the workforce (complete political suicide for the foreseeable future, but let's pretend) wouldn't really make a difference to the fundamentals. A child would still be a massive financial drain on a household and in the modern world people still have a load of other shit that they enjoy spending money on.
For a real change you'd have to look at stuff like completely axing pensions so that people would either need family to take care of them in old age or starve. Maybe a big relaxation of child labour laws so that kids aren't a huge net drain on the household until age 25. And a load of similarly radical policies that will be complete non-starters politically for decades to come. Realistically, things are probably going to get worse for a while before they get better when it comes to birth rates. Who knows what the future will hold.
