"Real communism" has indeed never been tried before. But, it probably can't genuinely become actualized in the idealized, most literal utopian sense.
"Real capitalism" has been tried multiple times throughout history and every time it both ends up badly for virtually everyone involved and also destroys itself almost overnight. That's kinda a paradox about capitalism---it needs constant moderation and control in order to actually function in a productive way. I liken it to fissile material where it is capable of producing immense wealths of energy if properly moderated and controlled, or otherwise it's an absolute toxic disaster.