They were brought up to demonstrate the gamut, that and to show how flawed the "they aren't even zombies" argument is.
Again you just seem to be sticking to a zombie trope that supports your argument.
No. I am sticking to THE zombie trope, and it happens to support my argument.
I welcome you to name any book or movie where zombies are depicted as problem-solving to the extent they are shown recognizing danger as danger and actively circumventing it. The closest I can think of is Bub from Day of the Dead, and I am pretty sure even he would blunder straight onto the spikes that lay between me and him.
In regard to zombies being clever, I honestly thought this was blindingly obvious; performance. Want a zombie AI which goes through a checklist of options every second or so? Sure, fine, makes the game run at a snail's pace. Want to remove that? Use the Unity navmesh and give them a direct route path. I obviously would prefer the former, and I do have issues regarding the latter, but it pretty much comes down to a trade off of "realism" or performance.
Now this made me chuckle. I wonder have you played A17 far enough to face a reasonably large horde when you have a large and complex base?? Every single time something gets destroyed (say a spike or some barbed wire) there is a huge and horrible "pause" where the game literally freezes for about 1/4 of a second. People have worked out this is the new AI algorithm recalculating the path for several dozen zombies.
You can even demonstrate how bad it is yourself, as follows...
I had a simple 4-sided base with spikes and whirly blades on all 4 sides. Every horde night was basically the same, they came from one direction and more or less attacked one complete side of my base. Then for day 42 I built a 3-block-high Iron Bars fence round the entire base. The difference on horde night was eye-opening. They would run at one side of the fence and attack all along its length. However the moment any block in the fence got destroyed.....horrible pause, as the AI recalculated the pathing*.
Surely if they just single-mindedly headed for the player at all times, the calculations would be much quicker and simpler? In addition, the player should be able to go round the other side of his base and have all the zombies follow him round, hungry for blood (as you could in A16 with a little effort). In A17 they will ignore that and stay entirely focused on the path of least resistance, even if that path is somewhat ludicrous, impossible or exploitable.
You are getting away from the initial point, it's not about people criticising the AI, it's that they somehow want development completely stopped and replaced by what we all agree is an AI that is equally unsuited for the latest build.
Why exactly do you consider A16 AI (with needed tweaks) as unsuitable???? It's definitely not performance, I assure you.
* this was not down to my PC being underspecced. I have every setting (except reflections ) maxxed out and I get 80 to 120 Fps solidly when playing, AND I am the host of a MP server. My PC can easily handle the game.