Art is truly subjective and I love it for that reason. My personal opinion is that art is a form of communication. To express a feeling, an emotion, something profound...visually. That is powerful to me and I wish it was something I could pursue in purity without worry of sustaining my living. Like a song, everyone feels something different when looking at a piece of art work. I love that you can evoke so many emotions from a single piece of work. Appreciation for the work in and of itself. What it tells you, what the artist is saying, what you say back to it.
There is a visually stimulating exchange that happens that is so different from hearing words spoken. An indirect conversation. I feel that is what art should be. Something that makes you think, makes you linger to contemplate sub-consciously. Art can be so subtle you don't even realize it whispered to your mind.
Anyway, think this was a good question with many answers. Each valid and worthy to be explored. A question with no answer yet many answers.