Thing is, it needed better done foreshadowing. It needed showing. Show her her having difficulty stopping herself when the blood and fire starts flowing. Show that whilst she has righteous ideals she has difficulty with reconciling them with her violent impulses *even* when it comes to civilians, as opposed to only against the rulers and soldiers.
Show her human heart in conflict with itself.Have a few scenes in earlier seasons where Jeor and Missandei have to remind her that these are innocent civilians and not their masters, and to bring her back to sanity. Because every time they show her going burny, it's always been against soldiers or rulers. Just something to give an idea that they are grounding her against civilians and things could easily spiral out of control without anybody around to ground Dany. Then it'd make her going 'f-it burn them all' feel more earned from the creators.
As it is, I feel like we got told "Oh dear she could become like the mad king", but never really *shown* that she was close to that edge. She always directed her hatred at those who she felt deserved it: at rulers who abused her and innocents, at soldiers who won't take the knee when given the chance, at criminals. Not just wildly lashing out. Aside from the choice of weapon, that's no different from any other GoT ruler and not enough to qualify as foreshadowing.
Though in my case, the Star Wars comparison would be for Anakin doing the 'I joined the Dark Side, time to kill all the little kids!' nonsense. I get "Dany's a Targaryen and they can go crazy" but this really seemed to skip all the signs of a slide into madness and looked more like someone tripping on a pebble and falling off a cliff rather than even a rapid slide towards madness.
At least with Anakin, it's something he'd done before. The Sand People killed his mother, so he killed them. And not just the men, but the women. And the children too!
And the chickens, oh yes even the chickens. The Jedi were (in his mind) killing his Wife, so it makes sense and is decently foreshadowed that when he gives into the Dark Side suddenly children become acceptable targets. Not amazingly well executed, but looking back they are least
tried to show instead of just telling you "something Dark side something dead children".
Yes, I am saying the Star Wars prequels did the slide to darkness and foreshadowing better than GoT just did. But I'd also take the Prequels over Episode 7 and 8 so...