Well then a planned command-style economy instead of a free market using Marxism as it's motivating principle. I'm guessing most of the western critics of capitalism aren't tankies, so they probably have in mind some sort of democratic ownership of production where people choose degrowth over profit. To the extent that's doable at the scale of nations is unproven. Potential problem is someone like Stalin or Mao will always subvert the movement for their own personal power.