He's an average coach. Let's be honest here, as somebody already mentioned, without JA17, his W/L record would be way worse.
If he doesn't at least lead the Bills to a SB this year or next, then in my book, he needs to go. Obviously, they should have gone to the SB last year, and they didn't, and that was directly because of terrible coaching at the end of the KC game. This year, because of the injuries, I might be able to give him a pass, dependent upon what he does for the rest of the year. As others have noted, his game day coaching is mind boggling at times.
And I hate when people compare McDermott to other coaches, by saying "he's better than many other coaches in the league." That's crap talk; we deserve the best.