TB I agree with you on this one, yet despite all the threads in which we have volified Michael, I think we have overlooked a rather weird form of idealism he maintained throughout his life.
This is revealed toward the end of GFIII when he tells Connie "The higher up I go the crookeder it gets." This tells me that despite his rationalization to Kay so many years earlier, and despite all his flaws, some part of him really did believe there was some kind of pot of gold under the rainbow of legitimacy. Of course his "default" position was always to resort to murder, but after Don Tomassino's death even Michael "couldn't do it anymore," and he handed the reins of the Corleone criminal enterprise over to Vincent. By that point he really was finished. I do not think, for example, he helped Vincent with the killings of Luchese etr al. the way Vito helped Michael plan the killings of the heads of the other New York families.