One thing Duchamp teaches us is that an artist is the one who makes something art. He was trying to mock the world of art, so he took an urinal, turn it around, put a seudonim and place it in a gallery. He was trying to do a statement and a critic about art, that art was anything you did. But the art world accepted the idea and it became art. It’s like when you as an artist do a stroke and it’s you who decide to leave it or to cover it, so you are the one who decides if it’s art. Another artist who tried to mock the world art was Piero Manzoni who packed his own shit and sell it (a friend said it was really cast). One museum buy it and made it art.
And that’s another important point. The world of art is not only artists and buyers, it includes curators, critics, museums and his staff, gallerists and galleries, etc, and is that people who also are the ones who acknowledge art and an artist.
Good or bad? That’s another question. I have repeated this many times. Art is an invention, so anything is valid as art. You just have to call it art.