But what you get instead is a much larger character arc for Michael, which doesn't need Vito's sequences intercut to come across. The point is that ever since the later point of Part I, Michael has embraced what he once considered to be evil; now he sinks further and further into that evil until he has nothing left of whatever was good in his life. That's why the opening credits for the Saga are largely composed of additional shots of Michael alone at the Tahoe compound, now in ruins; the entirety of the Godfather saga until that point is essentially him remembering what brought him to the sorry state he is art in the final scene of Part II: a lonely man with an empty life, haunted by demons he created and which he cannot expel.

The best way to describe the intent of the ending of Part II, and the Saga, is to hear Coppola describe what Michael was by the end of Part I: "At the end of the first film, Michael, who started as a bright-eyed, idealistic, beautiful, talented man with all the potential in the world, was turned into this cold, introverted, loveless, horrible monster who closed out of his life the person he claimed to be closest to him, his wife. To quote from The Magnificent Ambersons, he got his comeuppance." To make that absolutely clear to audiences who missed that point in Part I, Coppola drove it further for Part II, and further still for the Saga. This is why the last sequence before the closng scene is of a flashback to happier times.

What the Godfather saga really becomes in this format is a story about the decline and fall of one man's moral sense. That's what Godfather I and II are to me. Maybe they were ALWAYS that for most viewers, but this particular edit makes that muh clearer for me. The Vito sequences are merely prologue, and to intercut them simply to balance out the negativity is not necessary: sometimes the point is to immerse the audience in such feelings.