Because they are. They are all very bad at social justice, probably because no matter the best intentions, humans are going to fuck it up. China isn’t even communist, it’s capitalist through and through. They have lousy worker protections, banks, housing markets, stock markets. The USSR was as expansionist and militaristic as any fascist regime, just like the current Russian one. Korea is essentially a tyrannical monarchy, no real communism to be found there. Why do you think the first ones to go up against the wall after a revolution are the true believers? Because they know it’s all gone wrong.