I think we have to distinguish between different parts of the chain. As for recording, the traditional stereo paradigm may not be the best way to reproduce the original sound. The next part of the chain is the easy bit. Digital formats are sonically perfect. The same applies to the electronics that come after that. In both cases this is because they surpass the threshold of human hearing acuity. There can be advances in the electronics of the chain, but those have to do with electric efficiency, manufacturing costs and reliability, and not with the sound quality. The last part of the chain is where the real challenges are, with speakers and the room. The explanation is a simple one: they have to deal with the physics of moving mass, and the physics of sound in a domestic room. In my view there has been real progress in these areas. My current speakers are way better than their similar ancestors (Quad 2805 vs the original, and Harbeth P3ESR vs the LS3/5a). The CD has given us a source that does not suffer the low frequency degradation of a tone arm's mass (etc), opening the door for subwoofers that can cleanly reproduce the lowest frequencies of a recording. My current Quad 606-2 amplifier does not really sound any better than my more than fifty year oald Quad 303, but my current speaker combo of the hjigh passed Quad 2805s combined with a three MSO equalized subwoofer combo is way more realistic than my old Quad ESL57.
At the same time I must admit that my original system of half a century ago (Quad 33/303 and Quad ELS57, particularly after the introduction of CD) is still a pretty satisfying system. The real change as has been in the quality and affordability of budget gear. We have a garden room with a set of a Wharfedale Diamond 220 speakers that I bought for 125 euros, and they are so much better than what one could get half a century ago, and also so much cheaper in real terms. And what to think of streaming all the world's music for so little money?
At the same time I must admit that my original system of half a century ago (Quad 33/303 and Quad ELS57, particularly after the introduction of CD) is still a pretty satisfying system. The real change as has been in the quality and affordability of budget gear. We have a garden room with a set of a Wharfedale Diamond 220 speakers that I bought for 125 euros, and they are so much better than what one could get half a century ago, and also so much cheaper in real terms. And what to think of streaming all the world's music for so little money?