all art at the point of creation is "modern" art. It is modern art for the people that lived during that time. I am sure many people when they first saw surrealist art or cubism thought WTF ... the man's face is all distorted or she has three eyes. But now years later, people collectively have decided that works by Dali or Picasso have artistic merit and many people would pay millions for them.
The "modern art" movement definitely leans heavily on abstraction. It pushes the boundaries of art into new mediums (graphic arts, materials, etc). We should always continue to ask, what is art? How can one see art in new ways? The world would be so boring if people just copied previous works or styles, slapped their names on it and called it art. Yes, most of the stuff that is created now, 100 years from now, people may not remember or want. But there are pieces and works from artists now known and yet to be discovered that will be "stand the test of time" for whatever reason. Something like Pollack's pieces may not be to everyone's liking but it has people talking. This is ATOT, a computer/tech heavy forum and yet, a thread on modern art and Jackson Pollock is 7 pages long. I say that is pretty impressive.