Do you think majority of people living in 70+ year old houses have such luck that it satisfies everything you write about? Considering people I know, I doubt it. The upkeep can require as big expenses (not just financial, also environmental) as tearing down and building anew.
Do it right in the first place and it will be livable forever.
People are physical beings with well-known needs - warmth, protection from the elements, water and plumbing, privacy, comfort, sunlight, air, lack of health risks (fire, unsafe water, outgassing materials, damp, mold, etc).
A good solution to this problem will be a good solution a century from now, with minor modifications.
People should be less into ripping things up just because they get bored with them. Even if we reuse materials, the environmental cost of a new building is huge.