A lot of us don't forget those things. We either reject the assessment, or we keep the mistakes in context. For example, the blown challenge this week was undeniably a bad challenge. That doesn't change the fact that the team has been generally really efficient with it's challenges under Garrett. Penalty dismay? Not sure what that means, but setting aside any correlation between winning and losing relating to penalties, we just haven't been victimized all that badly by them. (We're 10th in the league in penalties called, and 18th in penalty yardage against this year, if anybody's interested).
I don't know how you're measuring the 'general lack of execution at a given time when leadership is needed' so it's hard to debate that. My guess is that you're talking here about the times you're annoyed that a play didn't turn out right. That stuff all just falls into the tub of 'stuff I'm going to blame on the coach when the outcome is not what I want or expect.'
Some of that stuff might actually be on the coaches, but not all of it is. Deciding which is which isn't going to happen when the natives are as restless as they are this week, though, that's for sure.