The same way MacDonald or any coach or coordinator says he has to look at the tape to see what happened on a given play before assigning blame.
Its not that big of a mystery and i would get flamed for it when Russ was here and i would post multiple sequential stills of a play to show how it unfolded and why thr play worked, but the execution failed. You can absolutely evaluate how well a QB is going through his progressions just as you can evaluate whether a playcall given a certain down and distance was a good one.
A good playcaller anticipates what a defense is going to do and provides the offense and more specifically the QB options to succeed. Lesser coordinators get caught in situations like Grubb was again and again where the QB was left on an island with protection that wasnt set, outlets that werent available and routes that relied on there being more time than what was reasonably available. Sure, that wasnt the case EVERY time, but if it wasnt the case the vast MAJORITY of the time, Grubb was would still have a job. There were so many times where you could see a defense was going to blitz on 3rd and say 4, and rather than having 1 or 2 options for Geno to hit quickly in the space the blitzung player was vacating, and chipping the rusher on the way in, we would just have receivers running medium and deep routes. That happened starting in the Giants game and never stopped.
Beyond playcalling, our blocking scheme as stupid. We got manhandled and looked horrible for most of the season trying to force our guys to run a constantly overmatched zone blocking scheme. Over the second half, we ran more gap concepts and saw more success. Thats a shift that should have been evident in training camp or at least early in the season. Instead we get plowed every week, struggling to run because we dont do it enough to force the defense to account for it, but also dont even deploy a scheme that best helps our personnell.
The failures of the offense this year were multiple fold from route designs that didnt challenge defenses or exploit weaknesses (its been discussed quite a bit that Grubb wasnt exoerienced in attacking NFL schemes and instead looked to exploit matchups) in the way they were playing us to just not giving the QB options to ATTACK a defense rsther than hoping protection holds up. Grubb neutered our passing game to a degree by taking DK out of the scheme as a decoy so that he could better work individual matchups. JSN was the beneficiary. Everybody else suffered. From the outside, it looks like JSN blew up, and he did have a good year, but he got those looks because thats how Grubb's offense worked. Attack a player or two or a coverage zone, but not the whole defense.
The run game was the same, trying to leverage individual strength rather than schematic advantage.
After week 4, when defenses saw what worked against us, we never adapted until our run game started working at the switch to more gap play in the run game.
These things are FUNDAMENTAL errors in the coordination of an offense and Grubb failed at them consistently.
Waldron understood at a general level how to attack scheme as was evident in the fact that our offense was one of the best in the league over the first quarter and a half of a game whike he was here. He could see schematic tendencies in a defense and script a way to attack them. He failed in the chess match that became that back and forth game of anticipation, move and counter move.
All-22 shines an entirely different light on games. What looks like one problem on a telecast is often shown to be something different.