Capitalism existed in the USSR as the blackmarket and the system of favors called blat, and it happens in prison. It’s the way that people get what they want, particularly in large scale societies. Markets where people sold things for a profit existed in ancient times and will continue to do so long after we are dead. What do you think will replace it? There will always be human waitrons at the finest restaurants serving the people who can afford to eat there. They won’t want their food cooked by a disembodied mechanical arm either.