Nobody talked about enemy count. The Survival Horror genre is a variation of the traditional adventure genre (monkey island, for example), and the enemies served a different purpose being part of a puzzle that consisted on pure inventory management. On the hardest levels of difficulty, in a true survival horror (RE:Remake for example) you had just enough ammo to kill a certain amount of enemies, and you had to decide which ones you would kill.
On ZombiU this situation can't be replicated exactly. It's a first person game in fact, so you can't have automated shooting systems that grant you 100% accuracy so you can plan exactly how much ammo you've got and how many enemies there still are.
In ZombiU you can perfectly miss a shot or two, in fact, your accuracy and ability to fight does matters to a certain degree, thus making it a different kind of game. Not a FPS, but not a pure Surival Horror.
Anyway, it's still the closest thing to a Survival Horror that has been released on those past years.
Being more action focused doesn't mean being a Call of Duty. Action focused means that the way you perform an action has an importance, the more importance it has, the more action focused it is.
On ZombiU you had the melee combat which was 0% action focused (you had to control the pace, but once you had it, you could kill any zombie without any fear of being hit), you could mathematically kill a zombie thanks to it, but the same can't be said when it comes to the non-melee weapons. That's what prevents it to be a pure survival horror.
