I think there's a lot of truth to your point about the QBs. We know there are exceptions and we know first hand. Last year we were on track to go 15-0 and then Tua got hurt, but really our lack of success last year was about the defensive struggles and not about Tua.There's a simple answer to this question: they have nailed the QB position the last 8 years. From Watson to Trevor Lawrence is about as good as it gets in college football. Put an above average QB on their team instead of those 2 and they don't sniff the playoffs. Watson (especially) and Lawrence bailed them out of so many games. Of course, they have talent at other positions but the reason they've been as good as they've been and a team like AU hasn't is the QB position..
So I'd add this: Clemson has had great QB play BUT ALSO their defense in recent years has outplayed ours.