think of it like Cuba or any poverty stricken place where you have a clever folks but most of the stuff is old and decrepit, and there are efforts to rebuild the world, just imagine how bad can it get when you have a 100 year war fought with modern tech, and a result there's a lot of "junk" and destroyed infrastructure, it doesnt help the fact that the cheap and easy energy of oil isn't there anymore (bio-fuels are a possibility, specially algae fuel that can be grown contaminated or sterile areas, they produce something similar to the typical petroleum after some treatment) and a wide assortment of other renewable sources of power.
in this world there are many rebuild efforts, but it will naturally be an effort that will take generations.
in fact, the novel i write, rehabilitating a pristine ghost town in a privileged place resource wise is the overaaching theme, and to make it more interesting, this happens what are now called the Alps