Ah....ok. Explains a lot. Kinda like “The Lord of the Rings” (although a huge majority of fans of Tolkein’s tomes loved the movies; gave Jackson a pass due to limited screen time, even spread across 3 movies) or “The Hunger Games” or countless other books-turned-into-movies. It’s VERY hard to please fans of the original books; almost impossible.
“The Hunt for Red October” was an exception....outstanding movie, very true to the book. There are others, but I have never heard of the book “World War Z” so I won’t be “upset” that the movie strays....but I can certainly understand why diehard fans would be.
This looks to be World War Z in name only. Fast zombies, instead of slow. Working like ants as a collective, not as mindless creatures. Just rubbish. At least the ones you mentioned followed the main thrust of the book. This would be like taking the Bible and turning Pontius Pilate into a sympathetic character...wait:-)