The Bills have played in exactly 2 coin flip games when the roster talent was about even.
The Bills beat Lamar Jackson and the Ravens in the divisional round.
The Bill lost to Patrick Mahomes and the Chiefs in the divisional round.
Every other game was the expected result based on talent + injuries.
It's not his fault that people don't seem to want to agree that Talent + Availability is the biggest differentiator between winning and losing in the playoffs, and the people tend to overrate the talent of their own teams.
The vast majority of winning a SB is luck of the draw in how the talent you get in the draft turns elite. What you CAN control is player culture leading to player development leading to player performance.
The Bills have an excellent track record in player development and performance. The 10% non-luck reasons for the Bills not winning or making a super bowl can be pinned down to Beane's FA/Draft choices, McDermott end of game situational coaching, his choice in coordinators and position coaches, and honestly mostly just the other team