I pretty much agree with everything but let's not pretend like there's no basis for Daenerys going insane, she's from a dinasty that's been practicing incest for thousands of years and with multiple examples of rulers going fucking nuts, her entire immediate family all went batshit over time, Daddy Aerys? Batshit, Viserys? Batshit, Rhaegar? Probably batshit to some degree.
They even alluded to this all the way back in season 2 when she has a vision of the Iron Throne covered in snow, which turned out to be ash instead.
Of course that's not to say D&D aren't fucking hacks and it wasn't rushed and very poorly set up.