There is no good or bad art. There is relevant, and irrelevant art.
In order to be able to say that a piece of art is good, it means that it represented something valuable at the time it came to be. It had a very specific feature needed at its inception.
Sometimes that’s something new, something no one was able to do before. Other times it’s something no one dares to do. And sometimes it’s just something someone needs at that point time.