I'm confused as to what isn't a "proper motivation" about the fact they're after your daughter because she has the power to allow them to invade other realities. The Wild Hunt wants Ciri for her power and we know that from the very beginning.
*shakes head
They are (1) the co-titular character, (2) the primary antagonist, (3) the main mystery of the series, (4) the character that has interacted with all 3 lead characters more than any of them have interacted with each other (5) a character prominent in the series.
With me so far?
They have 10 lines of dialogue.
10 lines of dialogue in a 200 hour game. The main baddie has more lines in the TRAILER than he does in the game. We get no more characterization of who he is besides other characters TELLING YOU who he is. He is THE MOST forgetful villain I have seen in recent memory, belonging more out of the stories written by teenage boys than a decent writer. Name me ONE thing that stands out about the Wild Hunt? One thing that makes them special? They are typically meat-head big bad guys, with no personality, no character, no depth and no purpose besides being a stand-in villain for freaking winter.
Even idiotic Marvel comic book movies have more depth to their villains than Witcher 3 affords its antagonist. If you think that's a sufficient character, I can't wait to see how your head explodes when you watch Citizen Kane or for a more industry-specific standard: Silent Hill 2, Portal 2, Half Life 2, Spec Ops the Line, and countless more.
It's like you are an apologist who can't admit any fault with the Witcher 3, particularly the most GLARING problem in the game