That's an interesting point. But it's hard for me to conceive of a morality based entirely on decision theory that doesn't essential resemble act utilitarianism. Maybe my understanding of decision theory is insufficient

Act utilitarianism bothers me as a moral theory. I can't demonstrate that it is false, but it seems to me that the perspective of act utilitarianism is not consistent with how we ordinarily analyze moral decisions. But maybe I'm excessively infected with folk moral philosophy.