I've read other analysis, the key point is ancient China always had an excessive working force problem, why inventing machines when your slave labor can work just fine? Things got worse when corns & potatos were introduced to China. A married couple can reallocate to really remote places and raise a family easily. There's no motivation to farming for larger margins. Silk and tea were much more lucrative business. Farming was scattered and limited to core-family scale. Tech advancements never caught on.