There has been exactly ONE game where the Buffalo Bills have underperfomed in a playoff game. That was against the Bengals in the divisional round. A game where they had a huge amount of injuries defense, and mentally they were seemingly broken.
Josh Allen played like ass. Stef diggs played like ass. The defense struggled to stay in the game (and they did barely btw - 17 - 10 half way through the 3rd Q). Everything fell flat and the Bills played well under their talent level.
Every other playoff game in the McDermott era the Bills showed up and played well and mostly played to their talent levels. That is the definition of being a good playoff team. As a coach all you can do is do your best to prepare youor team to play well, and then the rest is up to fate and luck. You can't control for Pat Mahomes playing like a football god. You can't control for the Chiefs having a flat out better roster in 2021. You can't control for having the entire gut of your defense not being available in 2024 and the chiiefs having an elite defense.
You give credit/critique of the things that your coach actually has control over. That's 2022 you can attack him for how the last 13 seconds of that chiefs game played out. But not really for the other losses