@engarneering @SecularJeffrey
I was born in '56 and your post just made me realize that I noticed it going on as it happened. I first spotted it in American car design and the rare Saturday cartoon I'd see (good friend had little brother) first, but couldn't put a name to it. I, too, wonder what the heck happened.
It was around the time that hilariously unsuitable-for-purpose plastics first started to be seen everywhere, like car interior dash knobs (which, if you lived in a warmer part of the country, would last a couple of years before breaking off due to sun-baking brittleness).
The majority of people stopped caring about quality all at once, somehow, or forgot that it had ever existed.