i am agree with you, North Korean back in 70 decades is much more advances society than PRC at the times. They were very industrialized, their people well educated compared even to South Korean. But their lack of genuine leadership and lack of vision and insight hindering much of their progresses and resulting in what we call today North Korea.
If I may also add, North Korea did not open up to the global market in the way China did. And thus , to quote the old adage, "Chosen remains ... a shrimp among whales..."