Replace "communism" with "centralized economy" and I think you make a fair point about a single CPU.
Communism can be centralized or decentralized (see the early definition of "soviet", which was a local and decentralized council-based power structure, intentionally created to counteract centralized Czarist influence... how full circle we've come).
Communism tends to give rise to centralized committees controlling the economy, but so can fascism, or even relatively benign democratic organs like the EPA. Communism has other faults, unrelated to centralization. Notably, the removal of economic incentive, and its replacement with wishful thinking about man's higher instincts to donate personal time and effort to fellow man, doesn't align with reality in either a centralized or decentralized economy.