I'm less concerned about McDermott than I am about the roster particularly on defense. It was built to win a couple of years ago and now has key pieces a little too old (Dr Poyer and Mr Hyde), injured and a little too old (Tre White), injured (Milano and Jones, and frankly Miller but it's not Miller time anymore). The Bills have made huge investments in their D and yet are going to have to rebuild a lot next year. The Miller contract, and not the Josh Allen contract, is the problem for a rebuild.
This all does come down to McDermott's shortcomings. The 13 seconds debacle was on him, but with a closer on the D line it wouldn't have come to that. So to deflect attention from his failure, McDermott got Beane to break his own rule about not busting his long-term budget, and now the team is behind the 8 ball, with too many holes to fill and not enough cash to do it.
I do continue to think poorly of McDermott for his lack of accountability and leadership when things go wrong. He just needs to take the blame when something is his fault, or even when it's not his fault. This is costing him with the players. As I've said before, players won't respect the man as a coach, if they don't respect the coach as a man. McD is apparently a great guy, caring about his players, etc etc etc, but he still needs to get out in front and take the shots and brickbats when criticism flows.