There seems to be a bit of confusion here between art and beautiful compositions.
Art is not art because it looks nice or because it looks like something else that is widely accepted as "art".
I see art as something produced by an artist combining genius + technique.
Genius usually implies being original, but also stating what the piece of art represents in contrast to the existing ones (what boundaries it breaks, what pre-conceptions it revolts against, what is its purpose (even if it's purpose is to have no purpose) etc.).
Technique means work and expertise. Sometimes genius is so overwhelming that there is little technique needed. Sometimes technique is so skilled that it overwhelms genius.
The makers of this app are probably artists (there's certainly a lot of genius involved in devising a way to produce such compositions, and work). What you create with your app probably not art though, regardless of how amazingly beautiful it turns out to be.
That's not to say artists may not make use of such tool to make art, but they'll have to find ways to be original. The fact that a button can be clicked to produce a result automatically destroys much of the artistic value of the outcomes. But hey, it's beautiful :)