had Germany gone communist instead of fascist, we would be living in a very different world
Depends on how long the communist moment lasted. Italy had a big communist movement in 1919, but it had fully collapsed within five years. The USSR was a dominant economic system across the world for nearly a century. It couldn't endure in the face of the productive forces of a capitalist rival.
I might suggest that a German communist movement was doomed in the face of the American, English, and French aggression. Especially if it was caught in the same kind of schism that divided Russia and China for so long. You get a Communist Germany that does about as well as Nasser's Egypt or Allende's Chile or Lula's Brazil. Or it gets watered down by perestroika as Gorbachev's Russia and Mandela's South Africa, such that it dissolves into a weak nationalist socialism.
Or maybe the Germans really did have the secret sauce to make Global Communism work, in a way Communists in Russia and India and Latin America and the Middle East didn't? I just don't think so. Not given how easily the country collapsed into the most enthusiastic kind of self-immolation.
I don't think there's any economy in the 1930s that was going to come off the plate, swing one, and do International Communism right on the first try. Maybe Berlin gets to be the center of the experiment instead of Moscow or Beijing for a generation or three. But it seems like there's still a lot of headwinds no matter where it started. Not unlike how liberal democracy and industrial capitalism had to sputter and fail and restart itself for centuries before it finally got enough traction to envelop the globe.