Look at the whole thing this way...Your world is not my world.
We may say an 'adult' is chronologically 18 yrs old, but the truly political being does not come to be until his/her early twenties after a few years of education, participation in the labor market, paid taxes, and a general awareness of how decisions by political leaders affect his/her life. Am willing to bet that your world contain a sanitized version of China, the Berlin Wall does not exist, neither does the mandatory Mao suit, neither does the Soviet Union, and so on. My world contains all of those things and more. If we meet a 19th century American, his world would contain institutionalized racism and all the things unknown to modern day Americans. Same for China.
North Korea and Cuba are remnants of my world, vis-avis the Cold War, continuing into yours. The problem for you in particular as an interested Chinese participant in this debate and for China in general is that North Korea is no longer useful for China other than the fact that NKR can serve as a geopolitical buffer against the US and allies in the region. A poor one at that. If wealth is artificial then the country is as artificially destitute, thanks to an odious regime, as South Korea is artificially wealthy. If the US is to share the credit for SKR's wealth, then China is share the credit for NKR's poverty.
Just as I cannot convince that 19th century American to my opinions of what is America, you cannot change my view because my world is historically more complete than yours.