I've considered that - and it's true in a way - the ones you see are the survivors. But it's surviving the trends and whims of size and style. And people wanting ice-makers and automatic defrost cycles. Not that like only 5% of the 1960 refrigerators were somehow built far better than the rest and they kept working.
I'm 100% certain that all 1960s refrigerators need repair eventually - but it's a simple compressor and that's it, one part probably fits dozens of models for 20+ years too. No sensors, controller board, ice-maker, fans, touch screens, seals, pumps, valves, etc. The difference is that you can't, at least economically, fix the newer appliances.
> every 2020 appliance you find in 60 years will be built robustly, probably in a serviceable manner.
true - but that number will be very close zero. Because there is not a single brand or type that is built that way today. If there is, it's some $10,000+ professional kitchen equipment. Sure some are better than the rest, but they are all essentially un-serviceable. We can mandate right-to-repair and force the vendors to sell parts for 3 years, we can't make them sell them at a reasonable cost. But in 20 years, somethings going to break that isn't worth fixing and nobody is going to stock specialized repair parts for your exact model.
> In any case, don't just throw these away! At least donate them to a nonprofit.
Have you ever tried donating a broken appliance? they don't want them and won't take them. Because they can't economically fix them either.