I think you can look at different lenses of success. Vietnam successfully defeated a much, much more powerful imperial force. They have fewer freedoms, and are still recovering from the generational damage dealt to them, and they are hardly without plenty of valid criticisms. But they've had successes.
China is a major global power. I think you'd have to accept that China is successful, even if that success doesn't reach every person. And I think it's fair to point at China and ask just how communist it really is. (Then again, I think it's fair to point at the US and ask how idealistically capitalist they are.)
Cuba has some of the highest literacy rates in the world, they have a developed medical care system with lower infant mortality, high vaccination rates, and they have developed their own effective vaccines for things like covid. They've eliminated measles. They enjoy a longer life expectancy than US citizens. And they've achieved those successes with an embargo that has made it difficult for Cuba to trade globally.
This is why I was probing for rubrics, because I think one can definitely find success in communist governments, and you'll also find corruption. And you'll find crime and war. And there's no clear story of "across all axes they are successful".
Would I rather live in any of these? It's complicated! I think there are very few countries right now that are primarily focused on the welfare of their people.
Vietnam is legit a good place to live tbh. My wife is Vietnamese and we visit at least twice a year.
Without making any value judgment on the government itself. I think it’s healthy for the planet to have people grow up in as many kinds of environments as possible. You know, as long as it’s not a full on totalitarian regime like North Korea or a place where women are treated like objects like anywhere ran under sharia law.
Currently, what are the countries that are most primarily focused on the welfare of their people? Those I would consider good countries.
I think it's useful to distinguish between political system and economic system. The traditional communist system was to have both a one-party state and state ownership of the means of production.
Vietnam and China still have one-party states but have transitioned to market economies. The fact that there are Chinese billionaires implies that they are no longer communist.
Cuba is still a traditional communist country--mostly because of sanctions. But they would love to become a market economy.
North Korea is the other one with both a one-party state and autarkic control over the economy.
Would I want to live in any of these countries? Absolutely not. I would rather be a median American than a median Chinese or Vietnamese.
I think it's plausible China and US invert in that calculus over the next 30 years. The median US person (anecdotally) feels to me like they are getting worse and worse stakes. $45k a year is not a lot these days. Chinese are investing heavily in infrastructure in a way that's appearing to build a healthy amount of economic potential. Whereas the US is... struggling. Global happiness index scores for China and Vietnam have risen dramatically, while the US is sliding down.
But I could be wrong. Maybe there will be a reversion.