I agree regarding the 60’s and 70’s. Huge gains in speaker technology, turntables, and then you had the receiver wars. I would compare all the monster receivers of the 70’s to the muscle car era on the 60’s and early 70’s. They can’t outperform modern vehicles but great lookers and still a lot of fun to own and use. Every town had at least one local stereo shop and a decent size city had multiple.
Then you have the dark ages. Started with the near death of vinyl due to the cd and the invention of 5 channel surround. You could hardly find anything that wasn’t black and the focus was running 5 and then 7 channel systems that ran double duty for movies and music play back.
We are now in another golden age though. Great speakers, huge gains in digital, tons of options for high end audio whether from the companies that weathered the storm and recovered or new boutique manufacturers. The only thing missing is you have to go to a large metro area to see great audio. We have your Best Buy’s etc but the small local shops are long gone. That’s a metro area of about 1m. Hard to compete with the internet.