This is why I recommended Clive Bell: for him the subject matter is irrelevant and what matters is significant form - that combination of colors and shapes that gives rise to an aesthetic experience. Many would say that achieving this aesthetic experience itself is the point. Alternatively, others argue that the subject of art (in this case urban life) allow one to get at the capital-t Truth and meaning of a thing or culture. Heidegger's "The Origin of the Work of Art" examines this with regards to Van Gogh's "A Pair of Shoes," also an interesting read. Of course the real point for anyone is deeply personal, and if you're questioning what that point is, for you there probably isn't one. And that's ok too.