The only people that think the problem with the Seahawks progressing was the QB are the same people that think Carroll can still be effective.
(ie wishful fans in Seattle)
You have to be wishful to overlook that Carroll isn't even good at the stuff he was good at in the past. Which leaves you with precious few strengths and a whole lot of weaknesses.
Even so, Carroll has a system that works on under .500 teams and he will likely use that. So we will be closer to bang average than terrible. But average QBs cannot make up for Carroll's deficiencies, and he won't have a great QB to win games against better teams despite Carroll's deficiencies.
Very few more come from behind wins. And we saw in how Pete used Geno, he still plans to try to keep the game close - those will just turn into losses against the better teams.
So your issue really boils down to an continuing and ongoing disapproval of Pete Carroll. It over shadows everything else.
And that's the long and short of it?