The legitimate gripe with Golson is that mentally he hasn't progressed seemingly at all, and has maybe even regressed.
He's late getting the ball out. Has been all year. He holds it until the receiver "wins" and then makes the throw. He also misses wide open guys far too often. The number of times Will Fuller has beaten coverage and Golson has completely missed him is sad, but even more sad are the number of times guys get wide open in the middle of the field and he misses them. I'm guessing height/sight lines are a large component.
Pre-snap, he's mentally inferior to where you'd expect a senior to be. He's only in his second year as a starter but he's had 3 springs and 3 regular seasons of learning the position. He has shown little or no ability to take "control" pre-snap... but this might also be on the coaches, as the whole "check with me" thing is almost surely by design.
Worst of all though, his leadership is terrible. Leadership is very hard to quantify and measure, but in short his body language is poor and he does almost nothing to take ownership/command of the offense. You don't see him demanding accountability from anyone, but that seems reasonable when you see the way he shrugs off accountability and tunes out Kelly on the sideline.
Your QB has to be a leader and cannot be timid or act shell-shocked. The only time I've seen Golson get animated and demand more from the team was against Purdue. Malik Zaire, by contrast, took vocal charge in the USC game the minute he was tapped to go in. He tried to get guys fired up and to give maximum effort.
I still think Golson is the starter next year and that he can be a great QB, but from Northwestern onward I have been really disappointed with how he exudes a "don't want to be here" type of attitude on the sideline... and how he still can't get the ball out on time to wide open guys.