You wrote: "If the team is not good at moving the ball and putting points on the board in the red zone . . . ." That is the crux of my issue with the stat ranking itself. FGs and TDs count the same for Red Zone Offense. A team could simply be incapable of moving the ball in the red zone and still have a high ranking per the stat because you don't have to "move the ball" to make a FG once in the red zone. Missouri 2020 is illustrative. Per the "Red Zone Offense" stat ranking that is linked, Missouri was #3 nationally. They scored a high percentage of the time they made it to the Red Zone -- 94%. But peel back a layer and you see it was a lot of FGs compared to TDs. They had 20 TDs and 12 FGs in the RZ on the season. That's fewer than two TDs per made FG in the RZ. Does that mean they had a "good" RZ offense? Doesn't sound that great to me. But there Mizzou is, in the top 5, according to the ranking -- along with Eastern Michigan, Northern Illinois, Kansas State, and Washington State.
I suspect what "Red Zone Offense" really comes down to as a stat are two things primarily: 1) not missing FGs and 2) not turning the ball over in the RZ. Both of those things are important. Don't get me wrong. You have to make makeable FGs (as a few have noted Doerer missed a few), and turnovers in the RZ are killers (Book's goal line fumble against Clemson sticks in my mind, though ND overcame it). But those things are very different than whether the coach "called the right play" or whether the coaches were "creative enough" or whether the team could "run the ball in short yardage." The Red Zone Offense stat, which sounds outlandish (ND is ranked #102!), doesn't seem to tell me enough. I think it would take a lot deeper of a dig to make sense of this.
Link: https://www.ncaa.com/stats/football/fbs/current/team/703