Abstraction in Modern Art

The last couple of years I've listened to my friends express increasing dislike and confusion with Modern Art, even the ones studying Art History, and there's something wrong when even an Art History major isn't sure what Modern Art is. The problem, I feel, is that the time hasn't been taken to coherently discuss what exactly is going on. Modernism is a very messy subject, my previous English professors willingly expressed as much, and often times people who lecture about it are so caught up in the idea that they forget to explain where the idea comes from.