In this Book, I dont know if the scene is in movie or not,
After stopping Delphi Diggory the niece of Amos Diggory,
Harry with his son Albus,Wife Ginny,Ron,Hermione,Scorpius and Draco, All of them see or atleast heard James and Lily die.
In a movie of Harry potter a scene is shown where it can be seen that Voldemort enters from the front door, so harry who already fought him can atleast delay the death of his parents (secretly with his friends) when he try to enter the house..
In this way His parents His parents best friends(Sirius,Lupin) Snape, Dumbledore could be saved and most importantly he could live with his parents live a happy and more life with his friends parents and he can atleast see or live with his real sister.
So in short did the writers actually told harry*s own mistake and more importantly he can live without tensions blames live without dursleys and cedric would have won the triwiazard tournament and the lives of almost half british Wizard community can be saved because they are in past and they can change it from then