Microwave ovens actually date from the 1950s, but they started to become ubiquitous all at once in the 1970s, when I was quite young. Within a few years we went from where most people hadn't even heard of them, to where anyone of moderate means was trying to figure out where to put one in the kitchen, about as quickly as DVD players made their way into our houses in the 1990s.
Microwaves have been standard equipment in virtually every kitchen for about thirty years now. There are people who have owned several houses and have children who never lived in a kitchen without one.
Sometimes I wonder if they look at a can of Spaghetti-Os and wonder, why do they still sell these in metal cans, when virtually everyone who eats Spaghetti-Os is going to heat it in a microwave oven, and yet you can't put the can in the microwave. Wouldn't it make more sense to put it in plastic or something? And of course they do, but only in canisters half the size but which usually cost more, so ultimately, the metal cans (of a typical can size) still remain the largest part of their sales (I assume).
And thinking that made me realize, my generation is the last one to remember when the normal way, in fact almost the only way, to heat up Spaghetti-Os, or canned corn, or virtually anything else in a can that needed heating, was in a pot over the stove. The idea must seem almost as alien as horse-drawn buggies to people just 5-10 years younger than me. In fact, the same is true of heating up most leftovers -- which means that there are tastes that are effectively extinct now, like that unique quality that leftover spaghetti (with sauce) gets when you reheat it in a pot, and it gets a little tough, but not in a bad way -- it's kind of hard to describe, you have to try it.
I suppose that if you really look, everyone can probably find something that their generation was the last to taste or try or do, and the advent of the microwave doesn't make that more true -- just more obvious. I wonder what other transitions like that aren't so evident.