> You'd have to be very wealthy to afford the lumber quality
For engineering purposes, you don't, since plywood and OSB are far more dimensionally consistent than the best of old growth lumber. Aesthetically, old growth wood is superior, but in most cases wood is covered in drywall & plaster anyway.
Old growth wood is just plain stronger than the type of wood you'd find in modern buildings. How much stronger? About 2-3x depending on the wood. Also, heartwood (from the center of the tree) is stronger than wood from the outer portions.
You cannot find (significant) lumber from 300+ year old trees anymore. That's what the original poster was referring to. I don't think aesthetics has anything to do with it.
> Old growth wood is just plain stronger than the type of wood you'd find in modern buildings.
That's true only if you discount engineered wood products, which are superior in strength to even the best of old growth lumber. For resistance to shear stress, nothing beats plywood or OSB; for bending stress, LVL; for tensile stress, LSL; for compressive stress, finger joined lumber.
For engineering purposes, you don't, since plywood and OSB are far more dimensionally consistent than the best of old growth lumber. Aesthetically, old growth wood is superior, but in most cases wood is covered in drywall & plaster anyway.