Derek Carr - Why People Dislike Him (IMO)

The difference maker that is ignored is Jim Caldwell being his QB coach. One season with Jim Caldwell and he got his first MVP but the system never changed.
And then Caldwell never went on to do anything with any other QB, save for an end of season stretch with Flacco that got Flacco paid. Interesting enough, they fired Cam Cameron and let Caldwell take over that season. I mention that because Cameron's only success came with Brees and Rivers.

In short, Manning continued to produce without Caldwell, but Caldwell couldn't continue to produce without Manning.
When you take this at face value, this is telling me that all of these coaches were/are able to produce with the QB that they named the starter. We could technically add another line for Lance since Shanny named his a starter at the beginning of the season and we can also do the same for Winston, since he was named starter.
I think it's more about the narrative that these coaches can just take anybody at any time and put up the same numbers--the QB matters. Purdy has made a lot of people forget how Shanahan did with Hoyer, Beathard, and Mullens (and I suppose Lance). Shanahan is 62-49 overall in the regular season, but it you break it out by QB, he is 9-29 without Purdy/Jimmy G and 53-20 with those QB's. It's a huge difference in performance based on who is taking snaps.

I wouldn't say that coaching is irrelevant, but I still stick to my idea that OL > QB > OC. Bad OL? QB will be severely limited. Bad QB? Coaching can only do so much, but the great QB's will be able to function in just about any system unless we're talking about having Peyton Manning run the read option.