We don’t know how good Joe Brady may turn out to be, but obviously coaching definitely matters. Andy Reid got rid of T. Hill and was left with Kelce, has beens (MVS) and rookies. The KC offense had its struggles and the team relied more on the defense but when the playoffs came they could rely on Rice and the others to make enough plays to win it all again. Reid had them ready to play.
As the OP stated, this team is mainly Josh Allen. He’s the only one teams have to game plan for. So, when you don’t have the marquee players, it comes down to coaching and scheming. Look at the Niners. They do have the weapons in Kittle, Aiyuk , McCaffrey and Deebo Samuel, but Shanahan also figured out that you could have receivers running around all over behind the line of scrimmage so he used that to advantage. By season’s end, a couple of teams copied that approach but I don’t recall seeing the Bills try it once.
Good coaching comes up with ideas that the opposition isn’t prepared for. Then, when the opponents adjust, you try something else. This can make your team very successful, even with just very good players.