The main thing I miss about "older" goods was the in-built design decisions, for repair-ability. I think, by the time I was born, food stuff had already started declining in quality. There was already information that farming soil was nutritionally depleted, in the 1940's. Clothing was certainly still better, but likely worse than what had previously existed. One of the more notable tragedies is the decline in vehicle quality. If I could pick the era of quality, for a vehicle, it would probably land between the 40's to the mid or late 70's (something with a manual transmission).
I think Amazon, as a focus for product decline, high-lights some areas of well deserved and needed attention. There are variables, existing in that scenario, that really only apply to Amazon. I think Amazon's methodology is just one example, of over all trends. In some markets there is very little option, for quality. In others, quality is only advertised/available where it is likely to be afforded. It seems to me that the decline in quality is an attempt to retain spending; this in the face of climbing inflation. If quality products replaced affordable ones the state of things would be more apparent, to the common individual. Instead, we see an increase in housing, some foods, energy, and transportation. With this increase we also see an increase in wages (depending on where you live), but this increase is "not" proportional to market inflation.
There are different methods of offsetting (at least perceptually) the disproportional increase in these financial variables. At the grocer, consumers may have noticed the increase in meat and egg prices (maybe a little with dairy). But, that increase does not enough express the actual inflation versus quality of product ratio. The quality of the meat and eggs has decreased, while their price still increased. If you look outside, of the common grocer, these products are even more expensive; in the case of meat four times higher, when previously being nearer to equivalent.
The increase in the cost of oats, as another example, is less dramatic. But that cost is offset by methods of growing. The use of pesticides is increased, to speed up the oat drying process. By this practice, the yield "per season" gained enough to offset the consumer unit cost.
It kinda looks like (despite making more money, by transitioning to inferior products) that the overall goal is to slant consumer perspective, on the actual state of inflation.
Some product actually remains at stable prices, helping secure a perspective of stability. Gasoline is a great example of this, as it's pricing gets lots of attention.