Computers have democratized production, but contribute little to the creative process. The ratio of "good" advertising art to "bad" advertising art is about the same as it ever was. The difference is that today "logo" creation is often delegated to a family member or artsy friend, whereas as in the past some less-than-inspired signmaker or printer would whip something up in order to get the project.
It is easy to romanticize the past, and there a plenty of beautiful examples of sign art done by master craftsmen. There are, however, many more examples of outright crap that never make it into the coffee table books and end up as part of the detritus of industrilaized society.
"Art is not what you see, but what you make others see."
~Edgar Degas