The difference for me is that, right wrong or indifferent, McCarthy was just growing a little stale. Not even just schematically, just as 'the' voice in the locker room. I think his voice grew stale, and I don't think he had total control of the team. It's been interesting to have several players come out and say that the locker room atmosphere is better, and that guys weren't being held accountable.
I have the utmost appreciation for McCarthy and what he meant to the Packers for over a decade. But it was time for new leadership and fresh ideas. You can just see the energy level revitalized. To your point, a lot of that indeed has to do with the Smiths and some of the acquisitions.
McCarthy should (and in my opinion will) be an NFL head coach again. And I'm sure he will be successful. But his tenure in Green Bay had simply run its course.
Also - not that this has anything to do with the above (or perhaps it does), but for one reason or another, the Packers were just quite simply never the same after the 2014 NFCCG. For what reason, I am not sure. But I think that was the beginning of the loss of 'fizz' or 'juice' as Rodgers likes to call it with McCarthy.