> A planned economy is certainly a lot more viable now than it was in 1950, let alone 1920. The Soviet Union was in many ways just a century too early.
If the economy were otherwise stagnant, maybe. But top-down planning just cannot take into account all the multitudes of inputs to plan anywhere near the scale that communist countries did. Bureaucrats are never going to be incentivized anywhere near the level that private decision making can be. Businesses (within a legal/regulatory framework) can "just do" things if they make economic sense via a relatively simple price signal. A top-down planner can never fully take that into account, and governments should only intervene in specific national interest situations (eg in a shortage environment legally mandating an important precursor medicine ingredient to medical companies instead of other uses).
The Soviet Union decided that defence was priority number one and shoved an enormous amount of national resources into it. In the west, the US government encouraged development that also spilled over into the civilian sector and vice-versa.
> But a major failing of the Soviet economic system was that there simply wasn't good data to make decisions, because at every layer people had the means and incentive to make their data look better than it really was.
It wasn't just data that was the problem, but also quality control, having to plan far, far ahead due to bureaucracy in the supply chain, not being able get spare parts because wear and tear wasn't properly planned, etc. There's an old saying even in private business that if you create and measure people on a metric they'll game or over concentrate on said metric. The USSR often pumped out large numbers of various widgets, but quality would often be poor (the stories of submarine and nuclear power plant manufacturers having to repeatedly deal and replace bad inputs was a massive source of waste).