The fight or the design of the monster wasn't the point of that bit of the story; it didn't matter what the monster was or even really what it did in the town, that was just the sci-fi wrapping to sell the Doctor being there in the first place. It was literalising what is said about the eccentric, 'mad' genius - they can see things in the world that others cannot. And tellingly, Van Gogh could see it but the Doctor, our 'mad genius', was as oblivious as Amy - a fact he acknowledged himself in the starry night scene. The story was about seeing things beyond the mundane or bland, not about fighting another kewl monster about to devour the Earth.
This.
