Well. I think plenty has changed since the 1970's, where my audio experience began. That's not to say there was no outstanding examples available at the time, but who bought them? Not many, and I'm including people who were actively into Audio, even High End Audio, in there.
I was there, we sold products like Quad ESLs, Magneplanars, Dayton Wright XG8's, Infinity References, Oracle 'tables, and yes ... Bryston (amongst others; I preferred the Threshold 400A and the Luxman tube gear but a 2B was a pretty sweet amp in those days).
But they were difficult to sell; although I don't mean to say they never sold, I mean you would not be able to survive as a business on those sales ... people listened and nodded their heads, but in the end they wanted the products they read about in the magazines of the day, and I don't mean the ad-free paperback sized Absolute Sound magazine.
Like today, the majority didn't trust their own ears and had to justify the expense to their friends with brands that advertised heavily. Just the way people are.
Still, I prefer and can hear fairly significant improvements in the modern examples of turntable, cartridge, pre and power amplifier, loudspeaker. Vast improvements in phono preamps, which were just emerging as a product in the late 70's, and loudspeakers.
Now, a 1975 Rolls Royce or Jag XKE or my buddy's '68 SS/RS 396/4-speed Camaro are remarkable automobiles, even today. But like the audio, they cannot claim to be the equals of *the best* of what you can buy now. What they do share with classic audio is the emotional "rightness" that makes them landmark products.
A modest "Classic" system can out-perform *some* gear sold today ... people today buy mass-market junk, or if I'm being harsh, rather ordinary but competent gear, that is buffeted by an advertising budget and positive reviews in Computer magazines (because that's what people read today) in preference to the truly remarkable gear.
But it's always been that way; if you want great gear that out-performs the classic stuff, you can find it. But you have to look, you have to trust your ears (few people do, in reality) and you have to actually fall off your wallet and get it into your living room.
With regard to "what happened to HiFi" ... I've said it before, but it's worth repeating ... teens today spend more on wireless contracts and cellphones than anyone I ever knew spent on HiFi, and if I had spent that % of my income every year from my teens until today I would have the five-figure components you see and can't afford in "Recommended Components" in my living room right now. And I don't.