> They claimed things are worse because we want them cheaper, but if price is adjusted for inflation, they’re of the same quality as always.

This is almost the correct answer, but the real reason is a bit more nuanced. There's a few parts to the answer, so I'll break them out:

So, as many people know and be-groans, businesses have been optimized by MBA-types who aim to extract as much value out of their companies as possible. In creating a product, that means giving exactly what the customer will purchase. In a competitive and elastic market, if you miss expectations, your customers will not be happy, and soon you might not have customers. If you meet or noticeably exceed expectations, you will have happy customers. If you unnoticeably exceed expectations, you are doing nothing but wasting money. You should spend your money on things that customers notice and care about, and stop spending money on things that customers don't know or don't care about, because they just inflate your costs, and ultimately, the final price of the product.

Designing a physical product is always a balancing act of cost, quality, and requirements. Designing a product with more robust components costs more. And the more robust it is, the more expensive it is.

Today, there are very good tools for determining how products will behave in the real world. Engineers are good at knowing how long a part will last in a particular application. Material science is more mature, and so is CAD and other analysis tools. There are also many more available materials and methods of manufacturing. The result is that engineers today have many more tools to enable them to design a product that is closer to their balance of engineering targets. If someone sets price, quality, and functionality requirements, those goals can be hit more closely than in years past, when there were fewer materials and fewer manufacturing methods.

Because of all of the above reasons, appliance manufacturers have been able to produce appliances that sell better. And in fact, the change in the typical lifestyle proves this -- household appliances that were once luxury purchases (which almost all of them were 70 years ago) are now expected in many households. There are many things that have changed in the past 70 years to make this happen. Prices have gone way down, manufacturing and material science has improved, new types of appliances have been invented, and new features have been added.

However, I think it's also important to remember that mass market appliances are designed for the lowest-common-denominator set of requirements. Most home consumers, demonstrably, are not making purchasing decisions based on a product's ability to last 70 years. Should they? Maybe, depending on how long they actually want to use it before it goes out of style and they throw it away. Would it be better for the world and the environment? Potentially, under the condition that it would actually continue to be used.

The bottom line is that most people don't buy heavy duty appliances because most people don't buy heavy duty appliances. However, heavy duty appliances DO exist! They're made for commercial market buyers who actually do put their appliances through heavy use and do have higher requirements for longevity and duty cycle. If you look at these appliances, many are built a lot like mid 20th century appliances.