Dany has shown a pattern of burning her enemies. Her enemies. Those that betray her, enemies in the field who don't bend the knee. Yet every time the thought of killing innocents comes up, she's gone extremely out of her way to avoid it. She kept her dragons locked up for years because they killed a single child.
There was plenty of development to have her destroy the Red Keep, and the horrifying thing would've been that she did so even though Cersei had filled it with innocent people. There was plenty of development to have her destroy the Lannister soldiers in the streets, leaving 0 quarter to the surrendering army.
There was no development to have her burn every inch of King's Landing and destroy all the people who lived there. There was no motive (Cersei pissed her off, but none of those people even liked Cersei), there was no benefit (none of those people would've cared who the Monarch was), there was no development leading to her personality cracking (your advisers deciding you're crazy and your nephew not kissing you right now just isn't enough to make you commit genocide).
That the ending the book is shooting for, almost certainly. D&D didn't earn it. Since they didn't earn it, they'd have been better off going with something else.
> Dany has shown a pattern of burning her enemies. Her enemies. Those that betray her, enemies in the field who don't bend the knee.
And people who by situation of birth are in a group whose way of of life conflicts with her moral preferences, even if they've never personally wronged her or owed her a duty of allegiance, c.f., Astapor.
> Yet every time the thought of killing innocents comes up, she's gone extremely out of her way to avoid it.
To the extent that’s even arguably true—at least, after Mirri Maz Duur in S1 (the negative results of which are the impetus for the one Stark example of Dany’s character development)—it was directly tied to a belief that she was loved (either personally or as a leader by the masses or, most often, both) and that acting otherwise would undermine that—a factor which very much was not at play in the attack on King's Landing.
And she's made very clear since very early on (though it's clear her practical expectation that this duty would be fulfilled has evolved over time) that she feels the masses of Westeros (and therefore those of King's Landing) do owe her a duty of loyalty that they betray by obedience to anyone else. It also made clear that her relative restraint was due to the restraining influence of a particular set of advisers and allies, all of whom were either dead or seen as betrayers (the latter—and in one case also the former as a direct result—in a couple key cases in part largely because their confidence in their ability to continue to restrain her impulses was slipping for reasons clearly shown in the narrative) by the time of the attack on King's Landing.
There was plenty of development to have her destroy the Red Keep, and the horrifying thing would've been that she did so even though Cersei had filled it with innocent people. There was plenty of development to have her destroy the Lannister soldiers in the streets, leaving 0 quarter to the surrendering army.
There was no development to have her burn every inch of King's Landing and destroy all the people who lived there. There was no motive (Cersei pissed her off, but none of those people even liked Cersei), there was no benefit (none of those people would've cared who the Monarch was), there was no development leading to her personality cracking (your advisers deciding you're crazy and your nephew not kissing you right now just isn't enough to make you commit genocide).
That the ending the book is shooting for, almost certainly. D&D didn't earn it. Since they didn't earn it, they'd have been better off going with something else.