I'm not gonna link the whole article cause it really is worth it to get a sub to the Athletic but this needs to be read (and there's definitely more in the article than just this):
From Jourdan-
https://theathletic.com/2356069/2021/01 ... ade-lions/
But in 2019 and 2020, there was a growing sense, according to people within the organization, that as defenses began to “solve” McVay’s widely acclaimed offensive system and he began to counter-adjust, that Goff was falling behind.
The Rams had the NFL’s No. 1 defense in 2020, but finished 18th in scoring and had the ninth-most inconsistent offense in the league according to the Football Outsiders variance metric. That inconsistency needled at McVay, and the Rams’ inability to put the pieces together on offense was a point of stress throughout the year.
McVay especially became frustrated with Goff’s turnovers — 38 in his last 31 regular-season games, the most in the NFL during that span — and even issued public criticism of Goff for the first time after the Rams lost to San Francisco in Week 12.
“Our quarterback has to take better care of the football,” McVay all but spat.
McVay’s decision to speak critically in public about Goff for the first time wasn’t just a sign of things to come, but also seemed to serve as a message to his locker room, where some frustration rippled during the latter half of the season — the message being that an underperforming player would not be coddled, regardless of that player’s status.
There was also some belief that part of McVay’s frustration stemmed from the fact that the changes he made to the offense this season, which were supposed to ease Goff’s discomfort when facing pressure and help him progress into higher-probability plays, simply did not take. The turnovers persisted, even though Goff totaled a career-low in air-yards per attempt as the offense opted toward those shorter, lower-risk concepts. The Rams also lacked a true “deep threat” receiver who could have stretched the field, but that was by design, because they were moving toward those shorter pass concepts and catch-and-run plays.