From a purely historical point of view, there's no way to understand what was going on in the 20th century without understanding the prominence, (lack of) quality of these paintings, and how they pulled the wool over people's eyes. It is true that people like Greenberg, Picasso, Pollock, Cage, Schoenberg, Rothko, Duchamp, and Warhol illustrate what was going on for 100 years, but that doesn't make what the produced or promoted something good or worthwhile. While modernism has indeed had some significance in the history of art for a time, that in no way implies that what modernists have been up to was actually good or artistically important. Fame and historic significance are not the same as making great art. The history of the 20th century wouldn't be complete without a mention of the activities of Stalin, Hitler, Mao, and Pol Pot, but that doesn't mean that they were good.