[BruceCroucshs]

For example, the Heart Sutra, in both is name and content, unambiguously identifies the place of Emptiness in Buddhism, that is, being the heartwood of the Buddha-Dhamma.

I feel this is why Mahayana is that... an "-ism", a set of ideals, ideas, a worldview, one more philosophy, one more religion... instead, the teachings of the historical Buddha are not about that but about a way to do something concrete to accomplish a concrete goal. If we are waiting for a worldview at the teachings of the historical Buddha, surly there will be a disappointment.