Stupid soldiers or denigrating directors
It's incredible in all these movies how trained soldiers are easily overrun by mindless zombies, but untrained heroes managed to fight them off.
Give an untrained hero a gun and he'll wipe out 20 or 30 beasts with little effort. Give a soldier a gun and he gets killed by the first beast to appear.
Matthew Fox takes out several with single shots at the end of the movie
Hollywood is so keen to denigrate the US Army - USAF are always wicked, insane, plotting, stupid, but rarely the good guys - that they never cope with a simple hoard of zombies. Thankfully islamists aren't as clever as zombies, or they'd have wiped out USAF in Iraq and Afghanistan within a week.