Socialism took the USSR from a late-feudal backwater that just lost the most destructive war in history (to that point) to the first man in space, and it did so in one generation and in spite of two subsequent invasions.

Socialism took China from a bunch of squabbling warlords dominated by foreign empires, where famines were regular and severe enough that people regularly sold their own children to survive, to a modern economic powerhouse, lifting a billion people out of poverty along the way.

Socialism took Cuba from a plantation run by foreign gangsters to cutting-edge medicine and higher life expectancy than the U.S., all while fending off a low-intensity war the most powerful empire in the world has waged against it for the entirety of its existence.