I once worked for a large corporation. In case this raw fact eluded you, large economic enterprises (businesses) are planned economies just like communist and socialist paradises. From this, I infer that I can learn much about potential weaknesses of the second two by studying the first.
This corporation decided that there is always one best way to do any task and that the best person to define that task was the person who does it every day. So they went to the person working on the line, in many cases a person who did not speak English as their first language, and directed them to write, step-by-step, everything they did. And they were suppose to illustrate the instruction book. And they were supposed to perform the time-and-motion studies. And they were supposed to analyze the optimum logistical flow and re-order levels. And....
The corporation had created the industrial utopia. The only problem was that only one production worker in twenty was capable of doing even one of those tasks.
The primary problem with Socialism is that for it to work in the long term it demands that 90% of the citizens be as altruistic as Mother Teresa (1-in-a-10,000)
Demonstrate the industry of a beaver (1-in-10)
Possess the self-denial of a religious zealot (1-in-100,000)
Have the absolute trust in authority of a child (1-in-3)
Multiplying these SWAGs together suggests that one person in every thirty billion will possess all of these qualities. That is four times the current population of the world.
Looking at the conundrum from the other direction, what economic system could possibly fail if 90% of the citizens demonstrated those attributes? Wouldn't they all be utopias?
Socialism is not so much an economic system as it is a fantasy about a population of Über-humans.