I really think the film was kind of cursed from the get-go. First, Joe Spinell died during pre-production, so they had to re-write the Willie Cicci part into Joey Zasa. Joe Mantegna did a fine job of playing the part, but the story lacked continuity.
Then FFC made the colossal blunder of being too cheap to pay Duvall (I still believe Paramount would have given him the money. I blame Coppola).
Then Winona Ryder dropped out, so Coppola had to tweak the script to suit his daughter a little better.
But I think the major problem was the redemptive theme of the movie. I posted this two years ago. It's Pacino's take on why the movie missed it's mark, and I happen to agree with him.
Pacino on GODFATHER III:
"You know what the problem with that film was? The real problem? Nobody wanted to see Michael have retribution and feel guilty. That's not who he was. The thing about the other scripts was that in his mind he was avenging his family and saving them. Michael never thought of himself as a gangster, ever. Not as a child, not while he was one, and not afterward: That was not the image he held of himself. So anyone who says to me that I played a gangster, I say, 'Not Michael'. He didn't come up that way. He's not a part of the GOODFELLAS thing. That's just not who Michael was. I've played gangsters ... but not Michael. Michael had this code--he lived by something that made audiences respond. But once he went away from that and started crying over coffins and making confessions and feeling remorse, it wasn't right. I applaud Francis for trying to get to that, but Michael was so frozen in that image ... Like he says to the priest, This is pointless to do this. but there was in him a deep feeling of having betrayed his mother by killing his brother. That was a mistake. And we are ruled by these mistakes in life, as time goes on. These crucial, brutal mistakes that we make in life. his choices--he was wrong. Like the way in SCARFACE when Tony kills Manny, that was wrong. And he pays for it. And in his way, Michael paid for it."
