The big problem with HotD's characters is that they have crappy motivation. When the show started, they all kinda sorta wanna be king in a vague, distant way, but they have zero immediate goals.

Compare that to GoT ep 1 where almost every character has a strong immediate, personal goal. And if they didn't have one is ep 1, they got one by ep 2.

And there were mysteries everywhere in GoT that had you begging to know more. HotD has no mysteries at all. None!

There are no white walkers, no "who tried to kill Bran?", no "who killed Jon Arryn?", no unknown schemers in the castle basement, no question of Jon Snow's parentage.

They just don't seem to "get" what made GoT good.