If you want proof that "hard work" isn't necessarily "valuable work," simply start digging holes in your backyard. It is hard work. At the end of the day, though, you'll have constructed nothing of value (unless you appreciate the value of holes).
But, as you see, value is a subjective concept. Communism believes it to be objective. But what's valued in communism is simply the biases of its architects. Resources, then, aren't allocated through an objective pricing system weighing conflicting values, but through waits, favors, loyalties, and fiat. Eventually, the system becomes so corrupted it fails.
We've objectively seen the failure of the communist system across cultures over the last 100 years. By now, there should be no doubt about its inherent ills.