Great idea for a post. Here are my thoughts on the items you mentioned:
Food Supplies Smart folks, who are likely the ones to survive the initial outbreak, would eat the perishable foods first. They would heavily ration their canned goods. And once they die, probably due to searching out for fresh water or trying to kill all walker, their stash of canned goods would be left behind. Making a great location to raid.
We have seen our heroes value fresh food supplies such as frogs, fish, deer, and even tomato seeds.
Your idea of concrete is very good. Logistically there are a few issues. There would be plenty of bags of concrete left in hardware/outdoor stores. It would cost gasoline(if you have any), time, and a great deal of physical energy to haul those bags to where you want them. Driving risk attracting walkers. And the concrete bags . So there is a very large risk factor associated with it.
The walls of woodberry are a much more likely situation. Aluminum roofing, wooden fence panels, and rubber tires would make excellent walls. Since Walkers can't climb very well, and aren't very strong, the easier the resources are to gather and assemble, the more efficient your wall would be. A town like Woodberry could probably make a wall of flipped over cars and tires in a relatively short amount of time, without nearly as much risk.
Collecting skilled people
Process of elimination. Regardless of who is most valuable, the bulk of the population has been eliminated. The first to go were probably uneducated folks not realizing there was a new virus out and about. The next wave would be the people who kept thinking it was just a virus, and the patients needed to be helped (The Herschell family is extremely lucky they have a swamp). After that would be the bulk of Americans that are just going to mind their own business as usual and stay away from the poor uneducated infected that are ruining everything. This wave is likely a lot of educated folks in middle to upper-middle class jobs.
Once those waves are gone, pure panic sinks in. Walkers aren't just seen a few times a week. They are around every corner. Your either fortify your house to wait it out, follow some evacuation plan, or go pure off to do your own thing. Out of those options we have seen survivors from all of them, but the bulk of the survivors have been runners. Not fighters, and not people fortifying buildings. The Hospital is the first look we have at a long term fortification that is successful. And they do collect skilled people. Having started with a collection of well equipped fighters, and kept nurses and a doctor on staff.
But my whole point is that a lot of the scientist, critical thinkers, and knowledgeable experts that could really rebuild society likely died because they wouldn't have paniced. They would have said that this is compared to other outbreaks they have heard, and even other rioting in other cities. Eventually order will be restored. They know panicing is bad. But it is panicing that saved Lori, Carl, Shane, and many others.
Kill all the Walkers
Risk verse reward. I think it only has a little to do with being tired. It seems easy for us to say kill all the walkers, but remember our characters see walkers all the time. Maybe the first 6 months they tried killing them all. But tomorrow they would probably see more. And they have seen many people die by simply trying to kill all the walkers in an area. And for what? It's never going to be safe? Why keep risking lives when it doesn't matter? After 3 years, I imagine they have come to the correct conclusion that battles, and battlegrounds, need to be selected based of risk and reward. Total annihilation is out of the question, unless you have an unlimited supply of ammunition, food, and water with a well defended base of operation.
I do think that our character are poorly equipped for dealing with walkers. At least the slow moving kind they have ran across. It seems to me that a machete, knife, and even sword is a poor weapon of choice. I think a sharpened walking stick, preferably keeping multiples on you, would be far more beneficial. Being able to stab with a 5 ft distance would be very valuable. Tree limbs are everywhere, and can easily be fashioned into sharp spears capable of destroying a walker.