Communism is a wonderful idea, in lollipop land.
Unfortunately, people cheat. And power corrupts, and ABSOLUTE POWER CORRUPTS ABSOLUTELY.
So any practical implementation of communism will fail, because those in power will extort those not.
Here's the problem. Group responsibility equals no responsibility.
What incentive does the farmer, for example, have to inprove her yield, year-on-year? Doesn't matter: the farmer gets paid the same as the doctor as the street sweeper: enough not to starve.
Sure, ever year the REPORT an increase, and because every one in the chain of command has an vested interest in pretending that the increase is real.
Under the Tzar, Russia was a net exporter of grain. Under communism, Russia was a net importer of grain.
Secondly, for the system to work, you have a principal-agent problem on the grandest scale, with all executive power centralised in one politburo.