Sound quality of Newer versus Older speakers

Newer, by far. Cone materials are far superior, even more so at the lower end of the spectrum. Ditto techniques for reducing varying inductance effects. Better capacitors. Far less cabinet resonances. More consistent dispersion.

all you say is true...however, if behind all that tech you don't put a engineer with an exceptionally good hearing and musical culture, the result is a round Zero. This is what happens to many companies...they focus on tech specs, even the wrong ones probably, aggressive marketing and fancy design. For those companies sound quality seems the last priority. In my very limited audiophile experience i know that dynaudio is one of them. They changed their priorities in 2016. In fact there are almost no happy contour 60 owners around. It's full of dynaudio fans which praised the old product lines and which agree the new product lines are a disaster. Despite better materials, better capacitors, better cabinet design (sure??? My contour 60 sounds like a wooden box emitting sound inside out). If you have a 10K budget for a speaker you can get crazy stuff in the used market.
 

I have a pair of new dynaudio contour 60. My fathers 35 years old crappy bose 505 sound more natural as my contour 60. I previously owned the Dynaudio contour 3.3 from the late 90’ which sounded far more natural as the contour 60. I believe there are a lot of modern speakers which sound more natural and balanced as the dynaudio 3.3 but i did the wrong choice.
What i’m sure is that at parity of investment you will get a better sound by buying older speakers. You find very good, top of the line speakers from 20 years ago for 1500 euro....to match the quality of those speakers with a new product you probably have to spent 10 or even 15.000 Euro. The contour 3.3 i owned costed me 1200 euro and they sounded ubelivably better (from every point of view) as the 10.000 Euro Contour 60. Speakers have a very long lifecycle.

It's like with everything else, like a super modern kitchen with a crappy cook, a F1 car with a crappy driver, 100mpx camera with a stupid photographer and so on. Technology has to be driven...it doesn't drives itself. Big companies are often driven by financial targets and less y passion and commitment.