Japan is learning as the rest of the world is learning, it’s not possible to maintain even replacement level birth rate in a society where women go to college and get jobs outside the home.
They won’t get married early enough, and even those who do will not have enough time to care for multiple kids.
The biggest problem is expecting people to keep pushing the requirements for a job before a person starts work. We need to bring back the guilds, where you learn along the way. Say 8 hours work and two hours learning, every day of your workday. This would allow a person to have his life and family and still have work.
For women, who really aren’t built for workdays, could stay home and keep the home while working part-time within the home.
There are reasons why society used to be this way, because it worked.
Even as early as 1953 there were cracks beginning to develop in the Japanese family. It was nice to see scenes of numerous schoolkids walking to school, but that was the beginning of the end for the Japanese baby boom.
"Tokyo Story" is considered by many to be the best film ever made. I don't know about that, but it was beautifully filmed and moving in parts. No monsters, car chases or superheroes, though.
Why is it a goal to "maintain"? Eventually it is self correcting and levels out.