I think most people are missing the major point as to why communism failed, as well as the defining charateristic of communism in general. We are all told early on that communism "is where everyone makes the same", but this is too simplistic.
Capitalism - output is set by the forces of supply and demand - this information is trasmitted to all by the price. If the price goes up, it signals to all producers to build more, and eventually, more producers to build the product. Just as importantly, if not more so, when the price of a good drops, produce less, and few producers build the product. After all if a product is not selling, this implies that to continue building the product (even if it will maintain employment in the short run) would be a massive waste of always limited resources. You may question whether the motives of the capitalist are selfish, or selfless, but at least they have some guide to go by.
Communism - Pricing model abandonded. Level of output for all goods and services are set by the Central Planning Agency. Without the information transmitted by price, the CPA has to in there best estimate guess how much of a given product needs to be made. Without price, the CPA has to know how the value of one good to "society" compares to another given the limited resources available. This requires complex understandings of how demographics change overtime, in both the long run and day to day. This is why you hear stories of the U.S.S.R overproducing some goods, like cement, while vastly underproducing others. The information required for any CPA to be successful, whether despotic or democratic, could never be available.