Keynesianism was the best economic tech,
Keynes wasn't socialist
if the state didn't fund education, there would simply be no education, despite near-universal private education in the US and UK in this time period, etc.
Just a function of most things being player-controlled.
The big problem Vicky had was lack of clear demarcation of what the player controlled and what "happened anyway". Was the player the government? A vague national Zeitgeist? Some sort of God? It was never clear. For example, IRL, more free economies had better economic growth. In Vicky, there isn't a GDP number that grows by a % each year, rather the player originally had total control over the economic system, which was simplistic enough to be centrally managed well. Later the Ricky capitalist system fixed this somewhat, though the choices of the capitalists actually tended to be worse than a "centrally planned" player-controlled economy and the only advantage was ability to spam factories cheaply: IRL, this was the other way around.
That more free economies had better economic growth is highly debatable. Germany had better economic growth for the latter part of the period than Great Britain, for example.