It's true, because that system worked for a few generations of people. A sudden change, even for a theoretically better system, can't make things better for people. Now we can see how much worse things became. Russia is completely deranged state at the moment, much much worse than Iran.
Communism never worked. People just survived it for a few generations. Who can say what europe would look like today if the Soviet union hadn't collapsed in 1991?
Probably would have been much better under communism for the last 30 years, if you want to go by comparing China's last 30 years of growth and prosperity and comparing that to my state's last 30 years of stagnation and methlabsperity.
the way I see it is that a country is better (or richer) if US allows them to trade with rich countries, not directly built on political systems, but political systems can affect being inclusive or exclusive of the global market.