Globally better means locally worse

Even when cars were new they couldn't be overbuilt the way buildings were in prehistory because they still had to be able to move themselves around.

Which is interesting corroboration in light of CronoDAS's comment that cars have been getting more durable, not less.

Home appliances have improved on measures other than durability

Older home appliances were also a lot more expensive in real terms (that is, controlling for inflation). Today, that same expense will generally buy you a "heavy-duty/professional use" version of the appliance that will be just as durable as the decades-old version was, and provide all of these other benefits for free. If anything, the real mystery is why these cheap, throwaway home appliances have gotten so popular all of a sudden. The general technological improvement you point to is actually a plausible candidate here - why buy an appliance that's optimized for durability, when in five or ten years you'll probably be shopping for a new model in order to get those other benefits?

I wonder how much of that is improvements in their manufacture (I suspect at least some) versus improvements in things like oils and other lubricants which then reduce the wear.

And cars are significantly more durable

That is an important counter-weight to the claims in the article I linked to.

ETA: Though maybe it's actually consistent in light of dogiv's observation that there were always limits on how much you could overbuild cars.

Quite - I have a 10 year old car and haven't had to do anything more drastic than change the battery - regular maintenance kinds of stuff.

I agree that a rich person won't tolerate disposable products where more durable versions are available. Durability is a desirable thing, and people who can afford it will pay for it when it's an option.

But imagine a world where washing machines cost as much as they do in our world, but all washing machines inevitably break down after a couple years. Durable machines just aren't available.

Then, in that world, you have to be wealthier to maintain your washing-machine-owning status. People who couldn't afford to repurchase a machine every couple of years would learn to do without. But people who could afford it would consider it an acceptable cost of living in the style to which they have become accustomed.

Planned obsolescence alone doesn't explain the change over time of this phenomenon. It's a static explanation, one which applies equally well to every era, unless something more is said. So the question becomes, Why are manufacturers planning for sooner obsolescence now than they did in the past?

Likewise, "worse materials cost less" is always true. It's a static fact, so it can't explain the observed dynamic phenomenon by itself. Or, at least, you need to add some additional data, like, "materials are available now that are worse than what used to be available". That might explain something. It would be another example of things being globally better in a perverse sense (more options = better).

the machine is designed to have a lifetime that is significantly shorter than what is possible, specifically to get users to keep buying a machine.

That's not what "planned obsolescence" means. Planned obsolescence means "if this machine is going to fail in X years anyway (because of one or more critical parts, or because technical progress means that replacing it in that timeframe makes more sense anyway), it makes no sense to design it to be longer-lived than that. So let's improve efficiency and cut costs by redesigning everything in it under the assumption that we're allowed to fail in X years, and any resources spent in extra lifetime are just wasted". What maximum lifetime is theoretically possible for any given component has very little to do with what's most efficient.

One can certainly criticize this sort of 'planned obsolescence' too, for instance by countering that modularity, repairability and lack of any single point of failure should be stressed instead. But let's at least get our facts straight here.

Highlites from the answer:

laundry machine from the 1980 did maybe 400 or 600 U/min for spinning while nowadays 1600 U/min is usual. Duration of a washing cycle has probably tripled (1 h vs. 3 h), and there are spinning cycles in between now, whereas there used to be only a final one.

They cite Miele engineering their machines for 5000 washing cycles or 20 years, while e.g. Whilpool, BSH and Electrolux use 2009 washing cycles and 10 years.

machines from the 70s and 80s needed about 4+ times as much energy (and also much more detergent powder and water) to achieve the same cleaning results as a machine from 2004

They find that 75% of laundry machines break at their first owner, and for those machines the average age went down from 12.5 to 11.6 years from 2004 to 2012/13. The fraction of laundry machines that breaks within the first 5 years has increased a lot (6 -> 15% of those that break, i.e. 4.5 -> 11.25% of all laundry machines).

there are huge differences between the cheaper and the expensive categories: e.g. after 5 1/2 years' equivalent, 25 % of the 350 - 550 EUR machines are broken, in contrast to 8 % of the > 700 EUR machines.

It seems that it's still possible to buy quality washing machine's if you don't choose a budget model.