Almost everything else is cosmetic, but some old construction practices can cause a bit of stomach-churning when you discover them during a remodel.
My 1901 Dutch-Colonial Revival has had a few of those. Like no headers over ground-floor picture windows -- the load from the second floor was simply spread across the shiplap sheathing to the studs alongside the windows. And no real rim joists, the floor joists were apparently held square during construction with more of the same shiplap sheathing on the ends. Survived a number of earthquakes and a broken foundation despite these defects. That old shiplap was amazingly versatile material, no?