If I'm not allowed to extract value, what is the incentive to start or invest in a business? Why bother owning or running a company?

I assume the parent comment meant extract as in vampiric. Collecting rents merely for owning assets rather than doing something useful.

China certainly allows you to get rich from starting a company so long as you're well-connected politically and/or obey the party. There is plenty of benefit to be had in a way absolutely not possible for someone in the USSR.