Well now the diffusion of tools has produced a more or less even playing field for everyone except Japan and South Korea are still working extremely hard and getting less sleep despite 2-3x higher GDP per capita than China.Of course you can have both; that's what China was having up to now. But that strategy is limited because space is limited; you can't just have 1.3B people ->1.8B people -> 2.5B people ->4B people all in the same space even with more highrises. And you shouldn't need to do that either to grow healthily. A good developed country has plenty of space for everyone, high standard of living, and it still beats the pants off of poor countries where people have 6 kids because the need for physical labor is so high. It is this difference in standard of living that allows developed countries to brain-drain poor crowded countries and a reduction will help ameliorate this as well. You need to reach a good equilibrium where it's not too crowded, life is enjoyable, and the country grows based on growth of the education and abilities of the average citizen, not just having more citizens, which is actually a burden when they are low quality. High quality equilibrium will have everyone working on cruise mode but the country still progressing faster than ever. How? Because once the country has developed a world-class foundation and technological tools, it can move much faster on much less effort. America has been on cruise mode since probably WWII but until recently, its tech was still moving faster than even China, which put so much more effort because America had better tools for tech development. 1 accountant working with Microsoft Excel beats a whole team working with pencil and paper. China paid in blood and sweat to finally develop and refine those tools for ourselves and once we use them to sit on top of the world, Chinese people too will find a fast-moving equilibrium larger and faster than America without grinding our workers to death working 100 hour weeks. The is China's end game; it is not to keep having more babies and working them to death (9-9-6 just to keep a small apartment wondering why they don't have more babies) for growth.
US is also not looking good as their physical tools - infrastructure - are getting old and difficult to replace and repair. EU has new infrastructure but just self owned with the sanctions.