The problem always was that the central planners never knew enough to plan the economy right. Well, with enough technology, enough reporting into the central database, they theoretically could know enough.

And that might actually work, if that were the only problem. But it's not. The deeper problem is that people work better when they get to share in the proceeds. People didn't work very well in the "worker's paradise". They worked half-heartedly, doing the least they could to get by, and production (and quality) reflected it. (This isn't exclusive to communism, though. Large corporations can have similar issues.)