Replacing people with robots certainly increases productivity, and frees up resources for other pursuits - it is also unlikely that the people whose jobs have been removed will find employment in many of these new jobs.

So sure, the entirety of the closed system (i.e. the Earth) has experienced a net productivity boost - but for the areas impacted (i.e. that part of China) this is very much a net negative.

This is probably the greatest social issue we face today. We are very rapidly replacing the jobs of tens of millions, if not hundreds of millions, of people. We are creating jobs elsewhere as a result - but the intersection of these new jobs with the skills of the unemployed is very low, and the nature of these new jobs also means retraining is becoming harder, not easier.