He's a true freshman. He's absolutely shook. He's lost confidence in the play calling and scheming. His receivers are not playing with enough urgency. He's not seasoned at all in P4 CFB, there is always a steep learning curve for a true frosh QB.
DR doesn't even get his feet set much at all anymore. He's got happy feet because he expects pressure and to have to be creative. But this goes against one of the main principles of being a good QB - you have to trust you blocking to a certain extent, while also using peripheral vision and keep tabs on an edge rusher bearing down. Being a QB isn't easy. Being a good or great one is tougher. Throwing off your base seriously deliniates from good consistent QB play. Sure, it is great if he can Mahome's it up when needed, but at this point he rarely has his feet set and his mechanics in line.
All of this boils down to coaching, really. Not just QB coaching, but offensive play calling/scheming, receivers running crisp routes, and the QB trusting the receivers to be at their spots at the designed (right) time. You can't have confidence to throw to a spot where the receiver is supposed to be, make that throw before the receiver has even turned his head or completed his route (DR was throwing to spots very well earlier in the season - so he knows this and CAN do it). Since opposing defenses now have the book on how to stifle DR and the Shitterfield offense, it makes it VERY tough on a now shook, true frosh QB, to settle into being comfortable.
Shitterfield needs to go. At the very least once the season is done, but for the last 3 games, since Satt can't dial up an offensive scheme worth a shit, hand the play calling keys to someone else (who would almost certainly be Thomas).