Believe me, it was plenty "real".

Communism fails for the same reason all Utopian schemes fail.

They all would require absolute power to implement, which inevitably leads to theft, murder and suffering, which, of course means that they are no utopia at all.

Nor do they mimic human nature, something pretty critical when designing an economic and political system.

Any system that precludes human nature in its calculus is doomed to fail.