Audiogon and the used market is not the cause of the decline of audio stores and the like. The used market has always been there with classified adds and newspapers of the past like Buy Lines. It is just that now you can search all over the globe. I am thankful of the used market as high end gear is way overpriced. However, it introduced me to high end gear that I could never afford otherwise. In addition, it has allowed me to pick and choose some higher end gear like my Luxman DAC that I bought new. I would never have bought it if I had not bought my Pass amp and BAT preamp used.
Home theater, Block Buster, video games, crappy music, cheap junk speakers and electronics that took off in the 80's and 90's helped ruin 2 ch audio. Same goes for streaming, walkmans, Ipods, MP3 also played a role.
Some good points but audio hobbyists and buyers of good gear have always been the exception to the general public and really 99% of consumers. Quality of music is not made for us, but for the general public and how they listen. 2 channel audio was not ruined by surround or some of the other things mentioned, what we do see always is the mass consumers drive entertainment, and high-end audio was not in their sight. Being able to find used gear so easily unlike 20 years ago. Time flies.
Audiogon created the online used high-end audio marketplace. Where you could look for anything you wanted and buy with just a click. That killed audio stores because you no longer were dependent on them. A high-end audio manufacturer told me once "The USA market does not keep us in business it's the overseas market". That is where their sales were the strongest.
I worked for Sony for 22 years and I was there from when we changed the way we watched TV by developing VCR we developed both VHS and Beta, VHS was our throwaway due to limited picture quality and other issues, but VHS when we sold the rights to JVS it took off, and one reason was nothing to do with quality or picture quality it was they mass produced them cheap ours were $800.00-$1,200 and they were built like it, VHS $300.00, with later super VHS higher but still inferior to the BETA format. But the mass consumer could afford them and whatever picture quality they had was a-ok. So to them, that was good enough. They had families to raise and their expendable income was limited. I see the picture on their TV and shake my head saying how can anyone watch that.
I love my hobby but I truly know how rare I am, my family and extended family are around 125, not one as any audio system worth more than $500.00, and many systems they have had for 30 or more and they were cheap. They think I'm nuts to waste money on audio. My one power cord costs more than any of their systems. I was blessed with the Love of music and that was what your system should be about music not just the status of the expensive gear.
They listen to music on the radio, car radio, XM/Series radio, and phones with earbuds for the younger ones. People want portable music, Sony developed that with our Walkman, and everyone I know owned one or more, buyers jogged with them, and had private music listening ability without interfering with anyone else around them, which was the idea that drove us to develop the Walkman before the Walkman boom boxes ruled for portable music you could take with you and listen outside of your home. They were big and heavy disturbing others etc. The Walkman freed people to take music with them and today it's a given that is the way most people listen to their music. Home Theater same thing it brings the experience of a movie into your home and millions must have enjoyed it because it took over the market and still goes strong. In fact, many audio stores today survive by adding that to their offerings to customers.
We are an audio hobby and a niche in the big picture like physical formats are. I know my Blu-ray player/4K player has a better picture than a streaming service but that's not the point, it's the ease now people can watch movies with a press of a button, so bye bye BlockBuster and others and needing own a DVD to watch a movie.
Napster started the decline by being able to download music for free, it was uncontrollable for many years, hurt CD sales, and hurt artists and record companies. No one saw that coming, if vinyl had been the major way of listening to music there had never been a Napster, so digital came back to bite them. Then Vinyl started to slowly be pushed again and now it is doing well but nowhere near what it was in the golden Era, what Vinyl sold in weeks is now what it sells in a year's time. That is due to the general public not having a need for it like we all did growing up when vinyl was all there was. Vinyl today is a Niche market and is expensive for good pressing made in limited quantities, like Audiophile labels from my early days in audio. The thrill of hearing a direct-to-disc LP is still in my mind.
But times change, and people go with trends and marketing. Even us Philes be it the hottest speakers, Streamers, and DACs (how many are there now) or amps preamps, and power conditioners of all types but the newest is the hot one and people sell their old stuff to buy the new stuff. Magazines do a great job promoting sales. And if you are into TVs the best ever comes out every year like new audio gear the newest is the best ever. The experience though sees you past that if you have been in this hobby a long time.
Today you have several downloading services or streaming services where billions of songs are at your fingertip and people rarely now listen to albums just songs they like. I still like the CD, they sound better to me, like Blu-rays or 4K look and sound better than a streaming movie. But you have to buy them and own them and the mass public doesn't need that. I grew up with Vinyl but no going back for me, I own too much music on CDs. Many will never be on LP and I don't miss Vinyl, but I miss having the large LP covers when they were like artwork in the heyday of the LP. Still, we boomers are the hobby, like hot rods, and street muscle cars.