This movie takes place almost twenty years after the first movie, and that world has been turned to dust. And like the other movies in the trilogy there are some unique lessons that can be learned despite its sometimes cheesy moments (It also has one of the most iconic soundtrack theme songs ever).
The First is just how quickly society (What’s left of it) will change. Those with the means and knowledge to gather and organize the survivors regardless of their social standing before will be the future leaders. In the early days of rebuilding things will take on almost a wild west feeling (Example Bartertown) laws are simple and enforced with brutal efficiency. Also don’t expect it to be anything fancy. At the very best it will simply be a re-occupied and fortified pre apocalypse town, at the very worst, some mud huts at the base of an irradiated swamp.
The second is never underestimating human resourcefulness. In Bartertown they managed to regain electricity and fuel cars with pig dung converted into methane, this renewable source would have made Bartertown the beginning of a town that would have become the center of a new trading empire, had Mad Max not trashed the place first. Depending on where people settle and the resources at hand. They may be able to harness wind, solar, or even hydro-electric power from a nearby dam.
The third is never underestimate human stupidity. Humans are capable of doing great things, but in the case of the third Mad Max movie we can’t seem to figure out that greed was the thing that leads to fighting and nuclear Armageddon in the first place, and it’s what leads to Bartertown loosing its source of power. I really don’t think that’s something will ever be able to get rid of, and it will probably lead to our destruction.
The fourth is just how fast our knowledge can be lost. In one generation the world goes from an advanced civilization to a tribal superstitious one. This is represented by the children survivors of a plane crash who rescue Max. Because they were so young at the time they never were able to learn what their parents had and so that knowledge was lost to them. What they did remember was turned into folklore and myth; they even had cave drawings like our caveman ancestors. If you think that’s far fetched play a game of telephone and you’ll see just how fast a message can get distorted through a small group of people. Even if the message makes it through, its meaning may be lost. The same is true for civilizations. If ours was destroyed tomorrow it would only take a couple of generations to go from what we know to legends like the lost city of Atlantis.
The fifth is that even in the worst case scenarios there is always some glimmer of hope, unless of course the world explodes, or those damm dirty apes take over.