What did change was the coverage of mass media.
Instead of relying on long and expensive genuine user feedback loops to generate positive buzz around a product, advertising manufactures that buzz directly. This is why is it everywhere, and influencers are just the latest innovation. Not because product quality/QoL reached a high point.
As someone who actively seeks tools, furniture and other consumer products from that period, I tend to disagree.
Let's take furniture. Mine was made during this period by Stickley in New York state. One cannot find commensurate quality today unless you wish to commission handmade pieces.
We have devolved to the point of disposable $5 extruded-plastic chairs, which may provide service for a time, knowing full well that the inevitable trip to the landfill is just around the corner. I reckon we're a ways past said zenith.
The subsequent decline in product quality was caused by advertising displacing genuine user feedback in creating demand for products, among other things (planned obsolescence).
You no longer needed to create a great product that people would buy and recommend because it is great. Simply skip the loop and go straight from A to B via advertising (fake buzz).
The Galbraith argument that advertising was a necessary technology that benefits consumers is a Big Lie. Advertising benefits large producers, while consumers suffer from losing their voice and declining product quality.
Also, when new, a lot of old furniture was quite expensive and families would save up for pieces. We get the benefit of that being used and transmitted now (though obviously particularly striking pieces will not have a reduction in value.)
While I certainly appreciate older, sturdy furniture (especially solid wood furniture as someone with some cabinetry background), I prefer modern lightweight materials, even if they last less long. They still last most of my lifetime which is enough for me. Marketing is not the issue, sustainable materials usage is.
The things today won't survive, that's the point.
There's clearly a cost-benefit spectrum between artisanal craftsmanship & throwaway consumerism. Balance is probably the best approach. It's time for the pendulum to swing back toward fewer, better items with a longer product life.
That and the shift toward psychological advertising in the wake of
Bernays. Closing the quality/opinion loop only makes sense if quality
is really a concern. Post-Bernays the gig switched to manufacturing
desire by attacking the self-esteem of the "consumer". The product
itself became largely irrelevant.