Not all the world goes on precedent, but I can't think of any athlete who got off his game for various reasons for 5 years, then, returned to form.
I mean, Watson was good in 2020, then sat out for a year, got in legal trouble, was suspended, came back, played poorly, injured his shoulder, played poorly again, then his tore his achilles, then did it again, took forever to rehab and viola, looks decent in shorts in spring.
That's quite the gauntlet. But hey, you never know. I don't think it fair to say he's 100% cooked, but, meh, I'll eat my hat if he's good again.
His only real hope is Monken, who has designed successful offenses for every kind of QB.