I can see why they regret the CDC episode. Just don't make people think about the hows and whys.
The problem usually comes from the headshot trope. It takes some serious imagination (or ignorance) to swallow that one. A body that has been blown apart by a fucking artillery shell may as well be Hershel's head laying on the grass, it ain't going nowhere. Fucking WWZ.
At least WD does give us zombies deteriorated to the point where all they can do is lay there and rot, and can get blown apart by blasting them with piss. And that seems to be from lack of ability to catch food, rather than just aging. Presumably a "healthy" WD zombie can live forever as long as it eats. But a cripple will just starve & rot away.
At least I pretend they thought about it that much.
EDIT: Also have to pretend that Michonne's zombie gimps would have rotted to nothing over time. And all those heads in jars that were still moving. God dammit, see what happens when you think? Better to be dumb.