Is that comparison similar square footage? I know of factories that have 10 employees and are small machine shops, and factories that have a few thousand employees (even ones that are highly automated). The difference is scale.
The factory I'm thinking of had 2000 people in 1950, and around 250 today - while producing the same amount of product. Automation is continuing to come to that factory - there are number of things that could be automated but their volumes are not quite high enough today to justify the upfront costs.