I'm disagreeing on the notion that Carr can't be coached to be an successful QB, as he was pretty good under Del Rio/Musgrave.
Also, if you look at the most successful QBs in the NFL, they are technically system QBs. We've done everything that we could to turn that into a bad phrase but the fact of the matter is. We've seen what happened when Brees left San Diego and came here to have a system built around and for him. We saw Peyton Manning bring his system to Denver. We saw Tom Brady struggling with Arians system and then turned about and implemented parts of what he ran into the New England system to the point where in 2021, Bruce Arians offense was pretty much pushed out the door. Every successful QB found themselves in the right system with good coaching. You would be hard pressed to find a QB that was able to find success with bad coaching and scheming.