It's not so much "Hollywood-izing" it, but rather story telling. You've built up a character as beyond evil. She's the reason our beloved Ned Stark is dead. You've set up Arya for wanting revenge because of Cersei. The cruel Joffrey is because of her, she brought the Faith Militant back etc. All of this is setting up the idea that SOMEONE is going to "get the rub" by killing her. Otherwise you might as well either 1) have her escape or 2) "win" the whole thing. Killing her off in the most meaningless of ways, almost redeeming her (at least she had her love with her at the last moment) is just bleh storytelling. You still want to drop a castle on her and kill her, FINE, but do it in a better way. Here's a free suggestion.
Cersei and Jamie are running to the tunnels. They reach the entrance and see the row boat sitting there. Both breath a sigh of relief thinking they are going to escape. The camera pauses and suddenly Euron emerges. Jamie screams at him "I killed you, how?" Jamie pushes Cersei behind himself and lunges forward to strike Euron down, only to miss. Euron strikes a near fatal blow to Jamie, who is on his knees choking on his own blood, fear in his eyes as he sees Euron continuing unbroken towards Cersei.. Euron walks to Cersei, who has relaxed, thinking she has control over him. She starts talking to him about how they will rule the iron isles and one day reclaim their throne. She reaches out to kiss him, to seduce him for her safety but feels something is wrong. Euron is Cold, unresponsive to her advances as he had been in the past. He reaches up and pulls off his face, to reveal instead it is Arya. Meanwhile, Dany's attack continues and the castle is falling down around them. Arya gives a short but poignant speech explaining that, by all rights she should kill her for what she (Cersei) did to her father, but instead has realized she just isn't worth it. That instead, she wants to thank Cersei for everything she has given her, how because of her she has become what she always wanted. And as a Thank You, she will give Cersei what she has always dreamed of, always wanted, always schemed to get, the Red Keep and the Iron Throne. As she says all this, she steps back as the castle ceiling collapses, crushing Cersei, who dies scared, alone, and destroyed by her own desires. Jamie, seeing all of this, lets out a soft moan of great sadness, choking to death on his own blood and the lasting realization that he has lost what is most dear to him (His sister and his child). Arya takes the row boat and sets off to Braavos.
Think about how something like that changes 3 stories. 1) Arya goes back to being a badbutt, deserving of having killed the Night's King, not gosh darn Arya Underfoot. 2) Cersei dies in a much more satisfying and cathartic way (even though it's still the same set piece of dropping a castle on her). 3) Jamie dies broken and saddened, having been defeated by a girl. All of this is much more in keeping with the character developments that have transpired over the last 8 seasons, not Deus Ex Screenwriter.