Not having Brando in the final flashback scene of GFII emphasized how disparate were the three (or four, if you count Tom) brothers in personality, ability, and faithfulness in contrast to Vito. Not having him there was a foretelling of how things might go when he departed this earth.

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."