I have the opposite impression: the multi-channel sound tracks on recent movies / animes is fantastic. Take Moanna & Coco by Disney, for example, this is sound engineering par excellence. Not on the compressed stream, but on 4K disk. They sound on my Denon 6500 way better than any Hi-Rez stream from Amazon HD routed via Chord Qutest, and by better I probably mean this extra immersiveness that extra channels give you.
Well that correlates with Toole's (and others) research and commentary regarding multichannel. Where I think the problem lies is that (at least with most systems I've heard) matrix processing of a stereo source is quite a different animal than sources which were mastered as separate channels to begin with. Although I think many of us are lucky enough to have multiple systems where one can enjoy both in their most optimal (within reason I suppose) settings - the holy grail would be a single system and expense which provided the very best experience regardless of the number of channels present in the source.
Now we just have to figure out how to get the companies to produce the thing that will eliminate any need/desire for future purchases from them - which is basically impossible. Even if such a thing
were possible, it would
never be allowed to leave the engineering lab (likely all samples would be destroyed and an iron-clad gag order issued against the engineers involved).
One suspects that the elephant in the room for home theatre is that for the most part the source material is way worse in quality than these AVRs. Movies do not aspire to ultimate audio quality. They have a very different remit. Moreover, most people only ever watch most movies once. Everyone has some favourites, but even then, the number of times they are watched is way lower than a favourite piece of music is listened to. People are just not as critical of movies. The experience in most commercial theatres is poor, and altogether too much in the way of modern movie sound is geared towards spectacle, not quality. This is a low bar for an AVR.
Now if you want, or expect, a high quality musical experience from your AVR, things have a long way to go. On just about every front. So far HT technology has made little useful progress in helping us recieve a quality immersive musical experience. Which is a great shame.
While I would agree with the
listening frequency aspect of your position - I would strongly disagree with the rest. In general cinema audio (especially recent HD & 4K productions) are engineered to a much higher level than music... in every aspect. There is more dynamic range - both used and available via the media itself naturally, but there is also a greater "quest for excellence" in my opinion which is often lacking in music production.
Certainly there are exceptions in either case (great 2ch recordings and horrible MCH soundtracks) but I do not think they are representative of the mean either. If for no other reason that the original source recordings are almost always SOTA for movies and often legacy masters for music invalidates the other side. Whether listened to once or dozens of times... our auditory memory is too short for that to make all that much of a difference - while the quality of the recording and mastering devices (and processes) most certainly does make a difference.
Though I would also agree that AVR manufacturers could do much better than they have, I don't think that is because HT users care less on the whole than anyone else... they simply have no other choices at the moment unless their budgets are well in the 5-figure range.