Why was protection of domestic industries from foreign competition criticized?

It harmed domestic industries.

The protection from foreign competition was also being criticised on the ground that it continued even after it proved to do more harm than good. Due to restrictions on imports, the Indian consumers had to purchase whatever the Indian producers produced. The producers were aware that they had a captive market; so they had no incentive to improve the quality of their goods. Competition from imports forces our producers to be more efficient.