I wish people would pay attention to the history of the Soviet Union instead of just using it as a whipping boy. What killed their dream of near-optimal central planning from the start was two things: firstly, the available computer power and communications bandwidth was nowhere near sufficient to optimize the whole economy, or to react to changing external conditions fast enough; secondly, they relied on people reporting what was happening on the ground, and most of those people had an incentive to *lie*. (Later on, a third thing killed them: that the existing productive systems had grown into empires and the people running those empires fought to stop them being torn down: also, by then the lies were so pervasive that not many people thought to tear them down. Capitalism's "creative destruction" may not be all it's given credit for but it's a hell of lot better than what they had.)
But the idea of optimizing an entire economy is not hopeless. You just can't do it with humans doing the data collection and reporting :/ in this it was very similar to much else about communism: it would work great if we were all selfless robots.
The nice thing about price signals is not that they are particularly brilliant or insightful. It is that they are relatively hard to manipulate, so individual liars can't bugger up your economy.