The entire system is based upon growth of the population. The population must grow constantly. Since the government cannot mandate reproduction, it must admit immigrants, lest we find ourselves in the sort of stagnation now afflicting Japan. Unions can deal with moderate immigration, but not with irregular waves of immigration of peasant farmers.
A lower rate of population growth could succeed using robotics, but the profits that come from the productivity of robots must be equitably distributed. as seems to have occurred in the world of Star Trek TNG and DS9, in which everyone has enough and no one seeks to dominate. This is utopian, and poorly described in the series.as a sort of background.