Sounds like success can come without an elite QB. I buy that. Good teams can be built with consistently disciplined play and upper third talent.
It can, but it requires the unlikely prospect of compiling enough talent at positions other than QB to compensate for the non-elite QB.
Think about it like this -- the 2016 Dolphins' passer rating was 95.5, slightly above average. Its opponents' passer rating was 88.5, right about average. A differential of +7 points.
That made them a weak sixth seed that got waxed in round one of the playoffs.
Compare that to the Patriots' passer rating of 109.5, and its opponents' passer rating of 84.4 -- a differential of +25 points. That much greater imbalance in favor of the Patriots produced a 14-2 record, a first-round bye, and home-field advantage throughout the playoffs, and we know what that led to.
Look at the difference there -- Tom Brady versus Ryan Tannehill and Matt Moore (who played well), and what that can do.
The Dolphins would've needed to have a defense that held its opponents to a passer rating of 70.5 to produce the same differential as the Patriots.
Now think of how unlikely that is. Between 2004 and 2016 there were a mere 20 teams of the 416 that held their opponents to a passer rating between 68 and 72.
So there is a mere 4.8% chance that the Dolphins -- given the level of QB play they had in 2016 -- would've performed well enough on defense to produce the situation the Patriots were in, heading into the 2016 playoffs.
So you can see there what a Tom Brady can do for you. If you don't have the likes of him, you need a highly unlikely level of play elsewhere to situate yourself in the most favorable conditions heading into the playoffs.