Personally, I was fine with how Lannister twins died in the end of (HBO-)GoT. People who cause the level of death and suffering like the Lannisters caused, they should receive no fanfare, no audience, no drama, to how they die; to give them dramatic &/or grand attention lauds what they have done, makes people remember them, and possibly even vindicates the horrible things they have done.
No, the absolute WORST thing you can do to monsters like the Lannisters is to have them die an unremarkable death, unseen and unlamented. To not be remembered, is the worst thing you can do to any megalomaniac (like Cersei).
I9 am absolutely not sensitive to this moral statements. Furthermore the La,nnister and Cersei are not horrible. They are fighters in a world where there is no law above the Lords. Morality means Christianity unknown in Pagan worlds.
But Cersei has to be killed crually for erotic purpose and Nothing else.