Hundreds of years later nobody figured out how to build things?

I love the Fallout series, going back to the original game. The whole “future as imagined in the 1950s” vibe is just iconic now.

But one thing kinda bugs me: How is it that a couple of hundred years have passed since the war, but nobody has figured out how to build things? All of the structures are either pre-war, or some ramshackle thing made out of old corrugated metal, plywood, etc.

I get not returning to prewar infrastructure and tech. But surely some of the survivors would’ve remembered how to use a level, a saw, a paint brush, etc?