In other words, 90% of everything is crap, both then and now. And thanks to Lindy's Law, you're usually better off buying something old than something new. But that's not how most people think :(
To take IKEA as an example, their table were really bad 20 years ago, and the only option was to either buy from another flatpack company, that was often worse (assembly would need like 50 screws for a single table...wtf), or a hand made "old fashion" table that would last a lifetime but cost 10 times more. Current IKEA tables will last a lifetime for the same price as the crap from 20 years ago.
Another example is French and Italian cars. They were really bad decades ago, reliability issues were only compensated by the ease to repair and cheap local maintenance. But industrial process are so much better now that production quality and reliability is at a level way above what would be expected for cars of roughly the same production cost.
Also, several of the more sturdy things they had they no longer sell and what they have now in the same category are vastly less sturdy.
I agree though, they do still have some good, quality, sturdy kitchen tables and a few pretty good sturdy sofas.
Makes sense!
I was also thinking there's a related rule - something worth buying used has proven itself to not be crap.
Another good way, check how much insurance costs. e.g. How much is that extended warranty going to cost on one car vs another. How much is home owners insurance in one neighborhood vs another. Insurance companies that make mistakes here go out of business.
Ice cream makers are one thing I have found that for. White Mountain made a really high quality product, but the used market is obscene, because people collect them apparently (at least in my part of the country).