I had the fortune of getting to rewatch the finale and while I disliked it less the second time around it was still incredibly frustrating. Back when I was on editorial and I had to edit stuff, I always had to ask young writers: "why did you add this line?" or "what purpose does this serve?" I kept asking those questions for so much of the show. Weiner wasted a ton of time. Maybe if it were a standard-length episode it would have been better focused, but almost everything could have been told more succinctly and dramatically than how it was presented.
Yes I'm about to repeat myself but our great payoff is that Don wrote a great ad. As lefty said: such wasted potential and as Bert Cooper said: who cares? If this show is that insular and that narrow-minded, then don't present it as some grand narrative arc of the 60s and the massive change to American society, it can't be both. Or, at the very least, have it pose some question, any questions really, about consumerism, identity, America, anything at all. But this show didn't.
While it was entertaining and I enjoyed large swaths of "Mad Men" it never really was about anything other than looking pretty with some excellent acting. That's well and good but not the stuff of greatness.