The white walkers thing was awesome as a looming crisis that would impact the world but was ignored by almost everyone until it was too late. Some of the best most memorable scenes still revolve around them. Jon seeing them for the first time and sailing away while zombies were born, them trying to kidnap one, the dragon being grounded and turned, etc. And the mystery of the Night King - who is he, how is he connected, what does he want - was an incredible plot point.
The problem was NK ends up being nobody, with no desire other than mindless domination, with no connection to anyone, who gets killed by someone with zero reason to be the hero. That’s why the WW stuff ended up being stupid in the end, because there was no meaning behind them or their leader.