I suspect the word dirty can be used to describe a lot more things today than it could 100 years ago. Some of these additions are useful - increased hygiene means less disease. However, a lot of the additions have no benefit, leading to time and effort being spent on cleanliness with no upside (and possibly even some downside).
A better definition of dirty could be:
The more dirty something is, the more likely it is to cause harm in the form of disease