Disability and Deformity
The Wasteland is filled with people who have both physical and mental disabilities and deformities: from the Wretched—who appear to be suffering from radiation sickness, starvation, and just about every other physical difficulty you could imagine—on up to the War Boys, a.k.a. Half Lives, who are doomed to early deaths by radiation, and all the way up to Immortan Joe, who is so sick he must wear a breathing mask. Mental illness and disability makes an appearance, too—just think of Rictus and Max.
So what's up with all that? Good question. Many folks have lauded the movie for it's depiction of physical disability as, well, something more. Furiosa, for example, manages to be a total boss, with or without the prosthetic arm. But others have noted that by making evil characters like Immortan Joe appear physically disabled in a grotesque way, the movie depicts disability and illness as something to be feared or despised.
Wherever you stand in that argument, it's worth noting that both the physical and mental disabilities present in Fury Road are almost always a direct result of the man-made ecological apocalypse. The denizens of the Citadel suffer physically and mentally because they live in a world where starvation, radiation sickness, and extreme physical harm are constant threats. That they suffer physically and mentally serves as the movie's warning that if we don't stave off environmental disaster, we're dooming ourselves to a rather wretched future.