You should compare countries of similar development. That's a good thing. People always compare the richest capitalist countries with the poorest communist countries, but by doing that always ignore the mass amount of poor capitalist countries, ones that are poor specifically because of capitalism.

Russia, for example, was extremely poor and behind. Comparing them to other majority agrarian societies during the Tsar makes way more sense than comparing them to countries that had been post-Industrial Revolution for awhile already, like Britain, Germany, or the US. That wouldn't make any sense. They were trying to catch up but they were still only just getting a proletariat from their burgeoning heavy industry and rail industries when the Revolution happened. They were way behind the West otherwise. Yet in a short period of time they managed to catch up.

China even more so was basically all peasants. Vietnam, Cuba, Korea, etc all the same, extremely poor, small, or both. So they should be compared with countries of relative equal development, which tends to be the countries in the global South, like Africa or Latin America.

Then there's the fact that they are kept at low development through purposeful exclusion from global markets, via sanctions, propaganda like the "Radio Free" programs, coups, support of separatist or terrorist groups, taking of national resources, being kept in debt by the IMF, and so on.