Home appliances, such as washing machines, are apparently much less durable now than they were decades ago. [ETA: Thanks to commenters for providing lots of reasons to doubt this claim (especially from here and here).]
Perhaps this is a kind of mirror image of "cost disease". In many sectors (education, medicine), we pay much more now for a product that is no better than what we got decades ago at a far lower cost, even accounting for inflation. It takes more money to buy the same level of quality. Scott Alexander (Yvain) argues that the cause of cost disease is a mystery. There are several plausible accounts, but they don't cover all the cases in a satisfying way. (See the link for more on the mystery of cost disease.)
Now, what if the mysterious cause of cost disease were to set to work in a sector where price can't go up, for whatever reason? Then you would expect quality to take a nosedive. If price per unit quality goes up, but total price can't go up, then quality must go down. So maybe the mystery of crappy appliances is just cost disease in another guise.
In the spirit of inadequate accounts of cost disease, I offer this inadequate account of crappy appliances:
As things get better globally, they get worse locally.
Global goodness provides a buffer against local badness. This makes greater local badness tolerable. That is, the cheapest tolerable thing gets worse. Thus, worse and worse things dominate locally as things get better globally.
This principle applies in at least two ways to washing machines:
Greater global wealth: Consumers have more money, so they can afford to replace washing machines more frequently. Thus, manufacturers can sell machines that require frequent replacement.
Manufacturers couldn't get away with this if people were poorer and could buy only one machine every few decades. If you're poor, you prioritize durability more. In the aggregate, the market will reward durability more. But a rich market accepts less durability.
Better materials science: Globally, materials science has improved. Hence, at the local level, manufacturers can get away with making worse materials.
Rich people might tolerate a washer that lasts 3 years, give or take. But even they don't want a washer that breaks in one month. If you build washers, you need to be sure that nearly every single one lasts a full month, at least. But, with poor materials science, you have to overshoot by a lot to ensure of that. Maybe you have to aim for a mean duration of decades to guarantee that the minimum duration doesn't fall below one month. On the other hand, with better materials science, you can get the distribution of duration to cluster tightly around 3 years. You still have very few washers lasting only one month, but the vast majority of your washers are far less durable than they used to be.
Maybe this is just Nassim Taleb's notion of antifragility. I haven't read the book, but I gather that the idea is that individuals grow stronger in environments that contain more stressors (within limits). Conversely, if you take away the stressors (i.e., make the environment globally better), then you get more fragile individuals (i.e., things are locally worse).