It’s a 60 minute game. It’s irrelevant how big of a lead you amass if you don’t win.
There is no realistic way to coach up Nixon, Valentine, Diggs, the CBs they signed off the street etc. so they do not leave receivers running open downfield. Why? Because they’re not talented enough players to do that play after play in the NFL.
Likewise, there’s no amount of coaching that is going to keep their D lineman in their gaps and their edge players in containment because they’re not talented enough to do it all the time.
Finally the players on the OL not being able to beat their man to create running lanes, and the running backs not being explosive enough to make the first defender miss are uncorrectable by any amount of coaching.
McManus wasn’t lined up correctly he didn’t land the kicks he needed to. No amount of coaching is going to make a 10 year vet change what got him to the pros.
So you’re right the Packers beat themselves, but it’s not by scheme, play calling or strategy. It’s due to lack of execution which always comes down to talent.