I don't blame coaching for issues like fumbles or players missing blocking assignments or things like that. That shit is 100% on the players. They're not coached to do any of that, and they just don't execute it. Seen it plenty of times in big games. Dropped passes, fumbles, sloppy decisions and turnovers, etc. Coaches aren't going to be able to fix that.
Where I see coaching lacking in some aspects is definitely in schemes, and in situational awareness. I look at stuff like Simpson sliding to recover a punt where he clearly doesn't have to. The schemes and coverage designs when you're trying to stop a team from driving 50 yards for a FG with 25 seconds left. Didn't like some of the offensive play calling late in the game. That's all coaching. That's the stuff that they can fix.
But there's too many "not quite good enough" moments in these big games for seemingly random players individually. Henry fumbles. Mark Andrews drops passes last year. Zay fumbles the year before. Lamar making bad throws/decisions at bad times. Corners or Safeties dropping balls they can easily catch for interceptions.
It's just weird.