China has succeeded so much by moving away from a planned economy when they were fully planned they were one of the poorest nations in the world. Most successful nations are mixed economies and yes, this is a settled question.
None of this is settled, because it's a living system that changes over time. What may have been perfectly true in 1850 might not be remotely accurate in 2050.
Then the soviet system stagnated hard under Brezhnev while the Chinese pivoted under Deng. But those first gains definitely happened under full communism and no capitalist economy has modernized faster.
The word you're looking for is "collapse". It's when something is stable at one point in time, but then later breaks down. That's what "changed". It wasn't random like weather or something. The economic systems collapsed.
> None of this is settled
The fact that it has happened numerous times in different parts of the world makes it pretty settled in my mind.