Art has a quality that is merely not personal and subjective. Interpretation is personal and subjective but if art was, then anything would do because there would be no objective-ish yardsticks to help judge between two random pieces. Postmodernism tried to explore the boundaries of how little is needed for the subject still to be art, which interestingly can be considered an art in itself. But the underlying current even there is that there is a human idea, motivation, or vision behind the art that is created. Computer generated pieces lack that; however, the process of computer generation probably does qualify as art. If an artist used a computer to generate images and make collages out the selected generated images that would be art—much like Warhol created art out of emblems of ordinary or entertainment figures.

I think the fundamental question here is why art requires a "human" element to actually be art, and what that "human" element actually is.

My opinion is that humans aren't really as special as we want to think we are, and that fundamentally there's no real difference between how humans create "art" and how machines create "art"; in the end, we're both drawing on our inputs, applying some subjective evaluation (possibly based on other inputs), and producing a corresponding output. How that "subjective evaluation" step happens might seem different enough to warrant different classifications, but I'm not really convinced it actually is.

Conversely, we can only understand, for example, animals' art to the very limited extent we understand animals: that is, we don't really have much of a clue if an animal doodling with pebbles in the sand is making art and trying to make a beautiful (to him) arrangement of stones, or just moving pebbles around for fun.

If we saw alien art, would we even know if it's art or something else? We would have to know the alien species, their culture, and how they live in order to even make educated guesses.

It might be that the concept of art likely carries over across species but we can only see in other species' art what is similar in our species.

If a monkey draws a monkey face we can understand that because we have similar eyes and we could draw a human face. But if we don't share even basic senses with some entity we can't possibly understand what visual art might be for them.

So, a machine producing "art" is something we can only understand as reflections to what a human would produce. We judge the machine's output by as if it was created by a human. But because we know it's not human made but just a compilation of random values and preset rules, it lacks the context we might call the human element and becomes void to us.

At a minimal scale the "human element" could even just be the story of the person who painted the image, even if the image is simple and not skillfully very refined. But if his paintings are a testament to how he after tenuous hardships ended up living on a small island and started painting, then we can reflect back to his story by looking at his pictures and try to see what parts of his life might be captured on the canvas.