Look up 'slow' in the dictionary. You'll find a definition of the word slow, which describes their service. Over 30 minutes for a pasta dish ordered at a counter? When the restaurant isn't even that full?
Now, if the pasta dish I ordered had blown me away, I would still be positive. But it just wasn't very good. It was more like a soup than a pasta, and not a particularly good soup, with a bland broth that attenuated the flavor of the veggies into a vaguely spinachy flavor. Not very good at all.
So, slow service + disappointing food = 2 stars.