- DPRK - Dynastic Dictatorial regime. Commonly regarded as one of the poorest and lowest quality of life nations in the world. https://www.bbc.com/news/world-asia-41228181
- China - see bottom of second paragraph in description section here: https://en.wikipedia.org/wiki/Socialist_market_economy
- Laos - Not the posterboy of the benefits of communism: https://freedomhouse.org/country/laos/freedom-world/2021
- Cuba - Likewise to Laos: https://freedomhouse.org/country/cuba/freedom-world/2021
Most of the people in these countries have reduced civil rights and do not get have much say in who rules them. Perhaps that is design intent, but I much prefer a system where people are free to make most of their own life decisions free of retribution and oppression.
Of all of your examples, I think Vietnam demonstrates the advantages of a planned economy, however, Vietnam is also a socialist-capitalist hybrid https://en.wikipedia.org/wiki/Socialist-oriented_market_economy and their people are also significantly less free than Democratic-Socialist countries such as Sweden and Finland: https://freedomhouse.org/country/sweden/freedom-world/2021
I mean Mark Cuban started by managing a restaurant, then starting up a TV network that did well. He’s no saint but he didn’t start with a silver spoon in his mouth.