I can believe that there's less of a difference when mainly comparing models of buildings. My opinion is based on comparing my Lego collection (primarily Expert Builder/Technics, Legoland Space, and general purpose Creator-like sets from ~30 years ago), and my son's collection (not as large, no Technics, mostly vehicles), which is at most a few years old. There is definitely a very big difference between those two collections. Also, my point (which I realize now I didn't convey very well) was not that there are so many unique pieces, it's that the diversity of non-unique pieces has greatly increased.