Well, my wife and I take good care of our stuff too, but the microwave still croaked (the transformer had to be replaced). I think they just don't make stuff like they used to. My mother-in-law still has her old 300 lb black dial telephones from lord-knows-when. Modern digital phones don't seem to last that long.
My dad bought mom a Microwave when they first came out commercially, for Christmas one year. I didn’t know what it was, it looked vaguely like a TV, but I knew it wasn’t. This must have been about 1973 or thereabouts. It was a Litton, I think. Early units used mil-surplus type magnetrons which were pretty powerful, later on cheaper stuff was used, but they seem pretty anemic. Commercial units seem to work real good - they will heat up a cup of coffee in about 10 seconds compared to a minute and a half or whatever.