Not sure why you are downvoted, this is pretty much spot on. The artificially low renminbi has been driving Chinese exports since the 90s and will probably continue to do so for the foreseeable future. Meanwhile the Chinese people got rapid industrialization at the cost of by and large living in polluted filth and crowded cities, and their per-capita GDP, which is a fairly good measure of the wealth of the median citizen, is still middling-to-terrible despite their high overall GDP.

This has been a great deal for the western citizen, who have been exchanging tons of currency for cheap goods(thanks to the low exchange rate), especially US citizens who have had their government's borrowing costs financed by the very money sent over there to buy things with. Not so great of a deal for the average Chinese, in comparison to what they might have had as a more westernized country.

Edit: Let's not even talk about the demographic collapse happening as a result of the one child policy. It will make any demographic problems in the west look like child's play.

You could also tell the very opposite story. In the last around 20 years, the poor and middle class in china greatly benefited from the economic growth, while the poor and middle class in the west didn't benefit at all or even had a wage cut if you look at inflation adjusted wages. China is hardly a developing nation anymore.

In economics you end up with a reversion to the mean over time. China was in a very bad state though terrible management over the preceding hundreds of years, so catching up was rather simple. US, is coming down from being the only modern state that was not destroyed by WWII.

US lower and middle class benefited from cheap goods, and suffered from continued automation and imports. However, the US produces more goods now than at any point in it's history so you can't really blame things on a lack of manufacturing.

IMO, I would blame 5 primary factors, massive undocumented population suppressing wages, developed economy making growth harder, tax policy's that harm workers directly and indirectly, unions shrinking, and rapid automation continuously disrupting the economy.