... Sophia Coppola was a poor choice & a weak point amongst an otherwise strong cast...
Are you counting George Hamilton among that otherwise strong cast?
... Luckily Pacino is good enough for the both of them.
I'm afraid he is not...if he were, we not continue be so focused on HER casting & performance all these years later.
...While i agree that many characters are more like carictures...
... They did fall a little short of what he seems to be aiming for, but not by all that much.
... Of course its pretentious, Michael & his cronies standing in the shadows..."this Pope has powerful friends. We may not be able to save him..." Of course its ridiculous. Now the first bunch of times i watched that, i would roll my eyes (like i would at other parts of the script) & wish they'd either left it out or worded it better. Over time though, the overly-serious-bordering-on-cheesy script came to seem fitting to the circumstances.
Whereas in GF and (especially) GFII one can find something new to enjoy and appreciate with almost every viewing...
If you needed to watch the movie a 'bunch of times' before ceasing to roll your eyes & finding some kind of explanation for the pretentious, ridiculous, bordering-on-cheesy script, then that's a problem right there.
Again, while your unshakable love and increasingly enthusiastic defense of GFIII (with or without the Mezcal) continues to be admirable, and while it is certainly not the 'worst' move ever made (that would be 'Titanic')...
For all the reasons you mention above, this film can NOT be defined as a 'classic'.
Apple