The Problem with Macro is Micro
John Quiggin makes the broad case (link fixed).
If you are then stuck with trying to present a Grand Unified Field Theory, you will inevitably lose (or, at best, reduce) the importance of all the agglomerations that follow from the presumption that the Rational Actor is the mean performer—ignoring that no one, including the economists themselves, believes that to be true in their own lives, let alone the lives of others.
Micromotives and Macro Behavior indeed. But no molecular biologist (or even biologists) would try to build on the Phlogiston Theory.