That's kind of the point. There comes a point where the organized remnants of humanity, who have now accepted what they are up against, can adjust and handle the situation. The question is whether they can keep from killing each other long enough to do so.
But, that's kind of the point. The organized remnants of humanity, who have now accepted what they are up against, STILL can't adjust and handle any situation.
I guess it's just easier to keep going to the OH NO ZOMBIES thing over and over instead of having to write in real drama. The writers make zombies inexplicably powerful, sneaky or smart when it suits them, and makes characters inexplicably weak, incompetent or dumb when it suits them. Basically, shit writers taking the easy way out.
What would have actually happened is Glenn would have led a competent, experienced, trained crew to the warehouse, not included the fucktards you could tell from day 1 were incompetent, they'd have swept the perimeter, killed the hordes in front because that's a potential threat, killed the shits behind the gate because that's a potential threat, not had zombies magically appear at the perfect times, climbed up anything at all when danger presented itself. But, then the writers would have to learn how to write real human drama, not just the oh-no-zombies or oh-no-dumb-human shtick they rely on over and over.
Fucking PUGs wouldn't exist, because you'd make sure the fuckers were up to par before you went out.
Example: the people on the construction site who have inexplicably been surviving this long wouldn't be completely incompetent, and even if they did get over run Who's-Deanna would have simply climbed on top of the tractor or pile of something or truck or ANYTHING above mouth level and simply picked off zombies one by one for as long as it fucking takes, because that's how easy it would be until the writers came up with more clever methods of zombie action.
The problem is the writing is shit, and when you have an episode like this where there's any action at all and a few good scenes of actual drama like the Preacher, people are like OMG ZOMBIES SO COOL and let the writers off the hook again for stupid shit like Carol deciding the fucking doctor has to die because he doesn't want her lesbo ass at his door asking questions. The better drama would be how do you reconcile the fact your doctor is a dirtbag, drunk, beating his wife but you need him, not what you know they're going to do and just blow it up making some bullshit point again about domestic violence, as if you just present it, then you're touching on some really dramatic shit.
Also, pro-tip: make a fucking spear!