Structure designs have improved allowing cheaper/more sustainable framing to be used that are stronger. Allowing a range of materials from simple pine framing, to block etc. modern wood framing designs can withstand a lot better storm ratings than even 20 years ago. Especially when you add things like hurricane straps in the south etc.

Roofing materials last longer and are cheaper and more sustainable able than old cedar shingles etc. modern sheathing instea of using massive 2x6 or 2x8, asphaul shingles instead of cedar etc. both better, cheaper and more sustainable.

Siding is better and cheaper and last longer. Again comparing any wood siding to hardy board over time. Vinyl in the right climate as well.

Electrical the same. Proper sheathed copper wire over shit like knob and tube or cloth insulated wire is cheaper AND a whole lot safer. Same with modern breakers, including afci and gfci.

Plumbing? Modern shchedule 40 pvc is a lot cheaper, and more flexible than copper. And even modern pex (when done right)can be even better and allow a single plumber to hump hundreds of yards of the stuff with one arm.

Drywall is better than that old plaster lathe stuff in most cases.

Insulation? Spray in cellulose and foam is infinitely better and cheaper, allowing much higher r values and a single guy to install over even the common fiberglass batten stuff of 20 years ago that was awful if you breathed it in or got direct skin contact.

Windows? Double pane vinyl with gas insulation is worse than the single pane blown glass? Come on.

Sure. Regulations and codes are higher and more strict. But that comes with the cost of most of the materials being better and easier to handle.

The fact that it’s cheaper is a testament to how houses in general are much bigger than they were in the 50s. But anything you build will always need maintenance.