I agree with this part and have been saying it for years. We have been experiencing this every single coaching change. We've switched to a 4-3 and back to a 3-4 multiple times and it seems that almost every HC change has resulted in that. When Rex takes over a top 10 defense and has to run his 3-4, my immediate thought was why? If he's this defensive genius that he markets himself to be, why can't he run a 4-3 defense and take advantage of what he has? Instead he blows the defense up.
The same goes for Dennis. We were a top rushing attack in 2015 & 2016. In comes Rick Dennison with his zone blocking scheme and our OL is awful. We were never a top pass blocking OL, but we had some good running holes. Those are now gone.
I do like Beane and McDermott so far. But the Dennison choice was a mistake IMO and I hope that McDermott shows this off-season that he's not willing to accept mediocrity and make a switch at OC, just like he didn't hesitate to make a switch at QB mid-season. I'm actually very happy they made the move. I've seen enough of Tyrod to know we aren't going to get very far with him due to his limitations. He needs a complete team around him to be successful, and when have we ever had that? Either we have a run game or a defense, but never both at the same time.
Dennison surely needs to go this off-season. We have so many holes to fill this off-season. RG and RT were in need of an upgrade all along, but to replace LT, LG and C because Dennison's scheme doesn't fit the players is foolish. Why choose him to be the OC then? Scheme should never be prioritized over players. The best coaches can adapt and utilize their skillset. When is the last time you saw Belichick force someone out because he didn't fit a scheme? He's the master at finding pro talent that isn't being properly utilized and taking advantage of it.
Like the move or hate it, McDermott showed some balls with this move. At 5-4, most HCs would have stayed the course until the season was lost before going to the rookie. I've been done with TT for a long time and wanted to see Peterman. I'm glad they made the move, but I was hoping I was wrong about TT as relying on a rookie with a tough upcoming schedule (west cost trip, KC, Pats x2) isn't usually the recipe for success.