Yeah, Dany went full Targaryen more than once, but we always rooted for her. She was always framed as the protagonist, and the music also underlined her big moments. I can't remember a moment where Dany went Dracarys and the score was underlying what a worrying situation it was. And, after all, she took down people we could see as "bad guys" - slavers, tyrants, rich corrupted people... there's a big difference in spending the series burning down slavers and rapists and violent rivals, and methodically carpet-bombing with fire an entire town that has already surrended. The worst she's done was burning down the Tarlys, I agree that it was a worying moment, but the slip to the "dark side" was too sudden for me, and especially without cause. If only the battle was still raging, if only Cersei was winning, if only some of her friends died... no, she went, won the battle alone in 10 minutes, and then with the city surrendering and no one posing a threat anymore, she razed it to the ground.
I would have welcomed a "the end justifies the means" kind of situation, but she burnt down King's Landing just because, and from her looks we were supposed to decipher that she realized all her family had lost and got pissed because of it (this comes from the authors as her actual motivation).