Another difference, not so much related to build quality as general livability, is that old houses were build before concepts like HVAC, mains electricity etc were a thing. Back in those days the idea of an ensuite bathroom was unthinkable and there was very little need for closet space.
My house once contained a rather unholy blend of original knob-and-tube wiring, ungrounded cable sheathed in something cloth-like, more ungrounded cable sheathed in something more plastic-like, and modern grounded 12 and 14-gauge cable. The plumbing is mostly copper for the regular water supply but the heating is a mixture of copper and cast iron, some of which dates back to when heating was powered by gravity. It's weird seeing a 3/4" copper pipe spliced into a 3" cast iron pipe. Trying to figure out how to run pipes, cables and ducts for air conditioning was something of a headache and the only options were either to sacrifice unacceptable amounts of space in the attic and basement, or come up with something that mostly works but isn't as effective as might be ideal.
These days people hang clothes, lots of clothes. When my house was built the chances are nobody hung clothes, clothes would be folded and put on shelves. In our master bedroom there's a closet that's all but unusable by modern standards - it has narrow shelves at each end so presumably the couple who used the room would both have space. Then in later years someone hung a 3/4" iron pipe lengthways along it to provide hanging space, but if you hang things on the pipe you can't get at the shelves without crawling under everything. Elsewhere in the house we have closets that aren't deep enough to use a hanging rail, so we have hooks on the wall in the closet so things can be hung. I imagine the kind of people who would have lived in our house 100 years ago would have had one quality outfit that was for church on Sundays, and multiple sets of working clothes. No need to hang anything at all, if it's pressed and folded well.