Sure, the only reason to see WWZ is the special effects, but that’s true of so many science fiction films that they shouldn’t be judged poorly if that’s their only positive aspect.
Indeed, given how many sci-films are only worth seeing for their computer-generated epicness or graphic portrayal of things you’d normally only see on a battlefield or in an operating theatre, then it’s to WWZ’s credit that it manages to rise above the usual awesomeness of contemporary animated portrayals of technological amazingness and extreme human and alien accomplishments.
So what if individual zombies make guffaw-inducing clicks and squeaks like a baby bird wanting to be fed, or if their teeth chatter like it was 5 degrees and you’d forgotten your thermals? Put 100,000 of them together, ramp up their speed and add some insane single-mindedness and they can accomplish anything together. Even a handful on an aeroplane are impressive enough that they require Brad Pitt to use a hand grenade to blow up the plane to miraculously survive them.
So gather all your preconceived ideas about zombie films, Brad Pitt and special effects and see WWZ. You will be disappointed. But only in the way you expect to be. The rest of it is all good.