Speaking as a craftsman and a salvager, I say-
I would sooner roof my shelter with aluminum from cans, than fell a cedar for shingles.
I would rather learn to knap plate glass than flint.
I plan to use swimming pool linings in the waterproofing of earth shelters.
We have to deal with the detrius of Civ by reuse, if possible… I expect organized mining of landfills in my time. This means learning to work with metals, even plastics. We cannot possibly put everything back where we found it.
(yes, we can drag every manufactured artifact to a subduction zone, and the Earth will eat it…)/{Waste nothing}