China's issue is more complex:

1. They're aging much faster than they're growing wealthy as a country
2. Their wealth inequality is vast. Japan is still in the top 15 for median household wealth (the US is 20 something by comparison)
3. A lot of the key metrics from China are opaque, smoothed, and questionable. Unemployment rates, for example are always 4-5% per government reports. Regardless of macroeconomic factors like recessions or economic booms. Those have multiple times been called out since they don't include rural or migrant workers, and some reports have suggested double-digit unemployment rates are common year to year.
4. China is still in the Middle Income Trap. The question is if enough of the wealthy urban coastal cities can generate enough to balance out the much more impoverished rural interior as a whole, and if they're willing to do so.
5. In contemporary history, the only countries to truly achieve high income status have done so with (relatively) liberal democracies, representative governments, and promoting progressive societal policies of various flavors. China is trying to break ground as a truly authoritarian police state wielding state capitalism strategically, and leveraging police/surveillance state technology to the fullest. To what outcomes very much remains to be seen. If they're successful, we may see far more iron-fisted style governments supported by, and emulating them. If they fail, it may be evidence that you can't turn a highly controlled society into a wealthy one, such as Singapore, at any real scale.