Maybe it was a mistake for New Orleans, but do you think Book is complaining? Doesn't change the fact Rees helped turn him into the winningest QB in ND history along with 2 playoff appearances.
The talent around Book regressed too. He went from throwing to Claypool and Kmet to a trio of Javon McKinley (Basically a blocking TE), Sko (Northwestern transfer), and AD (Converted QB). Love those guys for stepping up, lots of heart there, but not exactly world beaters as far as WR talent goes.
Hartman is not similar to Coan. Hartman set records. Coan was basically cast away by Wisconsin. Coan was a decent pocket passer, but I think we'll see a lot more from Hartman this year. Coan, Pyne, and Buchner are nowhere near Carr, Minchey, and Hartman. That's a stretch of biblical proportions.
We won games last year despite QB play, sure, but we also won games due to QB play. While not every game was great, Rees did manage Pyne very well at times and certainly got more out of him than he probably should have.