Thailand is a good example of an aging society that is at the precipice of developing and developed. When Thailand hit it's growth roadbump after the Asian Financial Crisis, they worked extremely hard at minimizing the urban-rural gap as well as expanding their social safety net.
If China uses the current slowdown as a forcing function for those kinds of welfare and inequality reforms, it can be expected to grow much faster and sustainably.
That is a choice to be made. Some people choose to be childfree out of preference, some out of economics, work/life balance, structural support. Even governments like South Korea, who have sunk billions into pro natalist policies, can’t turn around the total fertility rate.
The population decline is inevitable, better to get out in front of preparing for it now while there is enough aggregate productivity through healthy working age people, vs when this “light cone” perpetually shrinks and there is less and less people to put forth effort into needed physical work. The world will be fine with less people.
And maybe it's not a bad thing for the population to shrink gradually and through the free decisions of people.