Hi end audio equip sounds better today than in decades past due to tech - T/F

KLH 9s. Artjur Janszen. 
David rebuilds them in 2021 and his modern  designs are fine too.

Well, yes to materials and technology. No to the sound, good vintage is simply good. Individual choice.

Digital gear today is far and away superior to vintage vinyl, particularly on digital recordings post ca.2000. The same is not true for amps nor speakers, particularly at the high end

When it comes to amps, I would think that the passage of time treated tubes and SS differently.  There haven't really been any new tube circuit designs in decades, though some of Bob Carver's recent work might qualify.  As someone pointed out, if you were to update older tube gear, replacing aged components with new, where would the vintage gear fall short?  

SS may be a different story, with newer topologies.  That said, an awful lot of experimentation was done in the 70s and 80s.

Speakers have seen the greatest change, benefiting from discoveries and advancements in material science and manufacturing, as well as design and testing tools.

Pretty much everything I own is early 90s or older, except for the home theater preamp and amp, and a pair of speakers from 2008.  Most of it has been recapped and restored, tube and solid state.  Would love to try some new gear once I get my listening room set up.  Thinking Lyngdorf with RoomPerfect might be my first foray.

It is sad that there are a lot of audiophile here who don’t have any idea that records made from 1955 to 1964 sound best, much better than most modern digital records.
They don’t have any idea how do great sound speakers from the same era.
Most of modern speakers are low sensitive and have thermal distortion that most of speakers before 1970 didn’t have.
Thermal distortion lead to:
compression, different frequency response on different volume,
decreasing of magnet field on high volume, listening fatigue.