Manufacturing shirts are not single man task. Therefore there are lots of machine work and multiple man work is essential. In my opinion a garment manufacturing is the best combination of men and machines. Because you cannot get work done either only through machine nor only from man. But I agree a single man can produce a whole shirt from scratch, yes from cotton but it needs extra long time, which is not possible in today express world.
In our factory, I always research the pattern to walk them with the current fashion trend. I also well known about your curiosity to know the procedure of production of formal shirt. Following is the fast-track view of the one of the garment factory.