Isn't it more condescending to interpret the adults as if they _don't_ know what they're doing? How about seeing them as dignified enough to understand their behavior, and - oh, I don't know - make their own decisions?  And if the cast of the show is choosing to participate - and to be compensated, one expects,…

Ages?  It explains why Vito's number is so much 'higher'.  Also, Pacino and Caan would've been in their mid-late twenties during filming.  The obvious oddball is why Sonny would've been imagined as being younger than Michael, and also why Hagen was imagined as being the same age as Michael.

and Woody Allen to boot
I'd be careful about chalking up your angst to an 'indy/french movie trick.' That musicless, motionless scene at the film's close, outside of a school with an unassuming main character shuffling about, is right out of "The Piano Teacher," which steals it frame-for-frame from "Manhattan."