"Seen how they operate for 6 seasons?"
We've seen them less than 10 times in the entire series.
We know jack shyt about them aside from a handful of battle scenes, and the fact that they carry babies back to a ritualized area to convert them. We know they had some sort of pact with Craster, it's not a stretch that they will want another pact of some sort.
They aren't mindless zombies. HBO created an entire language just for them (the same dude who created the Dothraki language confirmed this). They want something, we don't know what it is, but it's possible it isn't a mustache twirling, "try to take over the world" pinky and the brain plot. Their motivations are one of the biggest mysteries of the series, Geroge has said this isn't evil monsters vs righteous humans, he tries to be more subversive than that.
I don't need everyone's plot to wrap up with the White Walkers. In fact, I hope the majority of the character arcs have nothing to do with them. Cersei's arc better not have shyt to do with White Walkers. Arya's arc better not have shyt to do with White Walkers. Let the fantasy shyt happen in one region and let the political shyt happen in another, and let the two parallel, compliment each other in a juxtaposition, like it has all series.