- Most of the stout, old growth timber has been used up, leaving shitty farm grown 2x4s as the primary stud material
- In the old days, they used rail road timbers and field stone for foundation and joist materials, nowadays they use spancrete panels and steel beams. Many floor joists in new constructions are that particle board infused dogshit.
- Lumber is smaller (1.5x3.5 is NOT 2x4) and spaced further apart. If you've ever remodeled an old farm house, they used to use reclaimed barn wood for wall studs and then use lath/plaster (which adds a lot to structural rigidity) in lieu of drywall. Everything was over built back then because they didn't want the fucker to fall apart.
- Many things were done by hand and therefore proper time and attention could be taken to do it right. Buildings go up in a fraction of the time it used to take, and you have trades stepping on each other's dicks trying to meet almost impossible deadlines that can be punished by hefty fines by the GC for holding the project behind.
I'm sure I could keep going but I just got off work and I'm tired as fuck. You get the idea. Bad materials, bad engineering, rushed work. Everyone is trying to save money and a lot of turds get erected as a result.