Carroll came into the NFL with a very unique prospective. As much as a disparage the guy now, Carroll was truly great in his prime of coaching. His background of being an NFL coach since the 70s that was coaching in the NCAA at a high level really gave him a prospective that not many other coaches have.
He coached against the trends that would become dominant in the NFL, long before they were popular in the NFL. Carroll also intimately knew many of the players that would end up being Seahawks. Baldwin, Kearse, Tate, Irvin, Browner, Sherman, Malcolm Smith, Thurmond, and Lynch were all guys that Carroll coached against every year, or guys he tried to recruit.
It was precisely because of that prospective that he was able to assemble the roster that he did in 2013 and 2014. I don't think any roster in the 2010s match the 2013 unit. It has been enshrined as one of the best defenses of all time and certainly the best of the 2010s.
Carroll himself would be unable to replicate that kind of success if he decided to rebuild everything. His insider knowledge of the trends that were to come in the NFL and the players that could execute have long dried up. I love Carroll, but it is sad to see him cling to his philosophy. It fit the bill for 2010, but the NFL has marched on leaving him behind. Carroll has reached the juncture of Holmgren on his way out. Holmgren said "I don't feel like I understood the game anymore".
The reality of the situation is, with Carroll or without Carroll we could be in for a long drought. Between Carroll's poor playoff showings and the Seahawks missing the playoffs 2 of the last 4 years, I think we're on a slow descent into the abyss with him at the helm. A new coach could face similar issues as Carroll. Just look at how many coaches don't pan out.
That being said... I still think Carroll is at his end here. He's done everything he's going to do for us and we've been on a slow descent into bottom feeder status for a long time. I've enjoyed his run, it's likely the best the Seahawks are ever going to have. It was magical to see the Seahawks in those moments, the amount of insane nail bitters and complete LEGENDARY events, how the whole city was lit ablaze. Carroll did that, he put that together and i will be forever grateful.