I disagree. I think many QB's, including Steve Young and Aaron Rogers, benefitted greatly by sitting on the sidelines, learning to become a pro. This is the way QB's used to be developed before the investment became so large that Head Coaches and GM's careers were tied to a young QB's success. Although game time development is important, so is learning how to control a huddle, locker room, etc. I believe a young player can learn to make better decisions by watching a veteran up close.
I am not saying his future success is a guarantee, but I believe he still has plenty of time to develop. Hopefully he will be better suited to succeed the next time his number is called.