Can anyone tell me where the progress in audio went?

Engineering at any price point is always a tradeoff. No, you "can’t have it all" most of the time - but you can have much of it. I think as others have noted that "technology" and manufacturing has reached a level people only dreamed of say in the 1950s and 1960s. As one guy mentioned this is a GREAT time to be into audio no matter what your budget is, from $1K to $1M. And you reach the point of diminishing returns pretty quickly as you go up the food chain. At some point you are paying more for the industrial design and "looks" than for a huge improvement in sound quality.

Look at digital cameras. Most DSLRs (and lenses) have reached a plateau in performance. Indeed, with mirrorless cameras pushing DSLRs into "old school" obsolescence. What more could be added? They already have more features than 99% of people will ever use, even a professional photographer. For the masses, their cell phones might be the only camera they will ever own.

And for some, it will always be (as it should) a matter of taste. Do you want the liveliness and dynamics of a horn speaker or something more refined and studio sounding. That was the answer Andrew Robinson gave on his YouTube channel when comparing the new Mission Audio 770 to the Klipsch Forte IV.

@moonwatcher , I would argue that lenses still have a long way to go, especially when price is taken into account :-)    Sensor technology has barely moved in what 7 or 8 years? Small incremental improvements but that is it. Even back side illuminated (BSI) are only a small improvement over front side with micro-lenses. There are some fundamental physical limits w.r.t. cameras. Look up Shot noise if you are unfamiliar.  I think computational photography is where mirrorless needs to go next. The processing in my phone is way beyond what is in my cameras. 

Back to your regular arguing (I mean programming) :-) [not directed at you Moonwatcher]

@moonwatcher, +1

Much of the progress is in profits. I would put a 1940s Shearer horn up against any of the greatest of today.

@moonwatcher ,

Perhaps with your camera analogy should be the recognition that some things you really can't improve or are as good as ever needed for human consumption. Look at pixel count. If you are not blowing it up and/or looking at a printed version close, 12 megapixels can display all the resolution our eyes are capable of picking up. You can add more pixels but you won't see any more as your eyes simply do not have the resolution.  No ones eyes have the resolution. The same is true of audio. This concept of "everything matters" has to be one of the dumbest things in audio yet I wonder how many people have typed it on these forums just this week? There are limits on what we can hear, let alone detect in music. They apply to everyone. There are minor differences but they are not all that great, and the main difference is training. This flawed idea has been used to justify all kinds of things are just nonsense and is used as a crutch by people to avoid accepting their own limitations. Just think if the spend in HiFi was redirected from all the things that make little or no difference into the things that actually do and the companies that do them?  Maybe it would make no difference, but given the op feels, and I tend to agree, that the industry is rather stagnant, change would be welcome.