In the 80s Americans were worried that Japan would leave them in the dust, yet they've had 30 years with almost no economic growth. Not exactly a great roadmap for China to follow. https://en.wikipedia.org/wiki/Lost_Decades
https://www.nippon.com/en/in-depth/a01001/
By 2060 Japanese children will be in the low single-digit millions, maybe 1/3 of the number when the experienced workers of the 80s were kids in the 1960s. There is literally nothing that can prevent it except mass immigration on a scale that would totally transform Japanese society (and which consequently will never happen).