Catholic Phoenix has a wonderful article touching on the prevalence of bad art (or, really, non-art) amongst the religious. As the article points out, this is because the nature (and, as a result, purpose) of art is not to tell you something--to push an agenda. Neither is art meant to make you feel anything. Good art does these things, but they are not essential qualities, but side-effects.
The nature of art is to re-create reality and the world around us in microcosmic form. Tolkien called it "sub-creation," because artists mimic God's act of Creation by bestowing form and shape on their imaginal vision. It is art's realism which makes it cathartic, as Aristotle says in the Poetics. Because of its realism, its incarnation in miniature of the world in which we live, art makes us able to live a second life through the art we ingest. In doing so, we feel the feelings of that second life and learn its lessons, sometimes hoping we won't have to go through what the protagonist did, sometimes hoping we'll get to.
Kitsch, propaganda, sentimentalist tripe is incapable of causing this, truly profound, experience to happen because it seeks actively to bring it about. In the end it only manages to shoot itself in the foot. True art is unconscious of the message it will put forward or experience to which it will give rise. True art simply seeks to tell a story, and the rest follows naturally.