Nowadays, women want to have more meaning in their lives than just being married to some guy they barely know or care about and raising his kids as some kind of servant with 2nd-class citizen rights. This isn't just in Japan, it's in every developed nation. The result of this is a far lower birthrate, so you can't have a super-high GDP for too long; you get a boost at the beginning because nearly 100% of adults can now contribute to GDP, but it burns out in a few decades because there's no one to replace them.
Societies need to come up with a new model.