1. Utilitarianism fails to understand morality. It isn't about maximizing the amount and number of "good effects". That's ridiculous. Putting to one side the psychopathic things that have been done following this line of thinking, the nature of morality is to be a good human specimen. That is to say, it is to live in accord with your nature, not opposed to it. Now, because we are social and rational animals, that will entail a good measure of acting for the good of others.
2. While we do have emotional reactions w.r.t. moral matters, morality is a matter of rationality. To fault utilitarianism with being "too rational" is to grant it a status it absolutely does not have and does not deserve. It is a defective understanding of morality that lacks rationality. It is irrational, in part because it also misunderstands rationality. Relying on emotion is not a solution to bad rationality. Why would they be? If anything, we have an obligation to align emotions with reason.