I won't quote anyone here, because there are several quotable posts here. So, just a few points:
First, the sanctions came down on USC six months after Carroll left. Was he warned that it might happen? Quite possibly, but the truth is that Allen came to Carroll with a boatload of money and total autonomy to run the organization how he wanted. Was Carroll supposed to turn it down? That is ludicrous.
Second, Russell Wilson's failures played the biggest part in the playoff losses. His slow crap starts while missing open receivers is what cost us in '15 (Wilson screwed us with turnovers and didn't play well until we were down 31 and the Panthers were in prevent), '16 (Wilson only led one sustained drive and hit one bomb that Richardson had to make an acrobatic catch to get us into field goal range until we were already down three scores, the comeback failed due to Wilson's interceptions) and '20 (I'm going to let Kurt Warner take this one: ) . The loss in 2019 was in large part due to no running game after we were literally signing retirees off the street due to injuries. The loss in 2018 was directly on Pete and a very poor game plan.
Third, the whole thing about giving McVay the edge because of their roster and knocking Pete for it is intellectual dishonesty at it's finest. McVay does not have the say that Carroll does on personnel matters. I'd also argue that Pete gives his underlings too much say as to who we draft. Everyone here accepts that Cable was given his druthers to draft poor linemen. Why not accept that Clint Hurtt has been the largest voice as to the linemen we draft since he became the D-Line coach? That means he is responsible for Malik McDowell's bust status and LJ Collier's bust status.
Fourth, saying that McVay didn't get anything out of Goff is also not accurate. Goff had three very good seasons under McVay. The problem was that the route tree got stale. People were jumping routes and some of them were poor decisions by Goff which led to quite a few interceptions. His supposed lack of arm strength was a big factor in the Rams moving him in favor of Stafford who could make all the throws.
Fifth, my answer for the question is McVay. I loathe some of Pete's coordinator choices. It has played a large part in the decline in the Seahawks. I also loathe the protecting of Russell Wilson's fragile psyche. McVay has made good choices in coordinators for years. He also shipped out Goff when it was apparent that he was not going to improve under McVay's system. He also knows when he needs to step back and part of what he is doing is not working. He also was able to get something out of Baker Mayfield who is trash.