Back it the day, you could just grab some colored soil from outside your cave, and draw some stick figures on the wall, and that's all you needed to make art. And museums would take it and display it. But no more. We went and over-complicated the process. Now you need paints and brushes and canvas (just try painting on the walls, and they will call it vandalism), and you need years of studying about color theory and perspective, and practice with models, and still museums will not take it.