It is easy to agree with virtually all you say (and certainly like the way you said it). But the opening sentence belies the body when you state, “The single greatest problem with large scale social change is that there is no single greatest problem.”
The single greatest problem is that antiquated print-era political systems we have, and which enables politicians to make their own rules governing their own behavior (especially in U.S. ), lack any interest in fostering large scale change (or for that matter any consequential change). To do so would come at expense of some one or group affiliated with the existing system. It would tantamount to asking those in the court of Louis XVI to tell Louis he need to abdicate in favor of a republic.
The more interesting question is why so few see this elephant in our collective room and think more rounds of musical chairs, with merely different names and affiliations, will either constitutes change or would deliver change. This is, of course, consequential because, as you indicate, the change we had is nothing like what is ahead.