I was going to suggest that a lengthy warranty would be a good guide, but gcb0 below says their LG came with a 10 year warranty which was worthless because it didn't cover one part.
Are customers even offered the option?
And why would "50 year appliances" have to be more expensive? The simple parts, and more basic processes used to manufacture them don't sound like costing more. And they could drop most of the electronics, IoT crap, and fancy features. If the average household could buy a fridge in 1970, why wouldn't they be able to afford one today?
Miele sells dishwashers.
And better made things cost more money for lots of reasons -- better materials ($$), more coats of paint (time, materials), heavier duty metals or plastic (time, materials, shipping expense), more careful manufacture, tighter tolerances, and marketing.
Experience tells us that the simplest explanation for manufacturer's behavior is the kind of malice called "maximizing profit, all else be damned".
That's Occam's Razor in use right there -- we would need to get out of our way to invent morally good businesses, incompetent engineers who can't get things to last, and modern conveniences that have short lifespans as necessary engineering tradeoffs to explain that away.