Very good points.
A lot of that applies to old industrial sites in the wilderness too.
It is not that they were deliberately booby trapped, it is just that they were full of industrial hazards back then, and then they were just abandoned to decay. They left pits to fall into, and things that could fall. I mentioned old open mine shafts, but even if they covered them you have no way of knowing of the cover will support you. Then there might be chemicals in leaking barrels, or maybe just spread out from the effects of time.
Caution is very important.
As an example you could step into some old shack and fall through the floor into the basement, or the roof could fall on your head.
Large piles of flotsam present the same risks. So do old log jams.
You really need to be careful.

One thing I did not see mentioned was old telegraph or telephone lines. These often went through areas that are no longer inhabited. Old telephone wire is usually about #9 steel wire. It is good if you need heavy steel wire for anything, kind of the big brother of haywire.

Old fence lines can be worth checking along.

I should mention that what I think of as useful in a wild setting is stuff that helps give me shelter, helps feed me or gets me found.

Yes the sides of roads are full of stuff like tools and car parts, but if I am on the side of a highway in a survival situation I would likely be more interested in finding something like a cop car full of cops.