There are several differences between the Stafford we saw in 2021 and the one we see this year.
Let me list a few:
The main difference between Stafford's performance in 2021 and this year is named Andrew Whitworth. Another is named Corbett, and another is named Edwards. Another is a healthy Brian Allen at center. Avila and Dotson are the best players on the line, and if they had a healthy Allen, less likely to get pushed around between them, and if they had a cloned AW on the left, they'd be a better line than '21. As-is, not as good and it's getting Stafford killed.
Creative and varied playcalling is another big difference in Stafford '21 and Stafford '23.
Stafford's arm is still plenty capable and the best it has been in a while. He's not up to peak physical level of his halcyon Detroit years, but still... he can wing it and when not injured because of a missed block (on a stupid play to begin with) or the hammeringthat occurs when somebody whiffs and he gets slammed on his hip, he's a more discilplined player than through his overall '21 campaign. Still a gunslinger, but one who makes fewer mistakes by putting the success of a play wholly on his shoulders.
He'd be a better quarterback with better protection and better play design and game planning. The DC's around the league have seen plenty of McVay tape and adjusted; what fooled them in '21 ain't neccessarily gonna be as effective in '23. The HC/DC persona with DC-in-name-only arrangement has run its course.
Fix those things and watch Stafford suddenly "rebound." He'd be comeback player of the year.
So what's the problem?
It ain't Stafford.