Part of this is down to the explosion of material sciences in the mid 20th century. Up until then things were mostly "made to last". Then plastics arrived and

Part of this is down to the explosion of material sciences in the mid 20th century. Up until then things were mostly "made to last". Then plastics arrived and "modern" became fashionable (and never left.) Handed-down furniture, appliances et al became "old". New meant plastic, or electric. Neither of which are suitable for longevity. The post-ww2 population boom (literally, the boomers) also placed strain on supply chains. Volume became the most important attribute of production, from houses to pencils. Again, longevity need not apply. The wheel will turn. But it may take some time. And precious little post 1950 will ultimately survive.