I feel that the AV-receiver market has gone the way of the DSLR market. Compact speaker systems like Sonos (that don't need a separate AVR) simply got good enough. Thus the need for buying a separate AVR to drive your Dolby / DTS / etc. setup has all but vanished except maybe for the most determined audiophiles (and even most of these would do well to simply get a compact wireless speaker setup instead of some monstr…
Sonos still has severe limitations and I regret buying two 5.1 setups from them. As a simple example: there is no 7.1 support at all and the Atmos support is a sort of faked 5.1.2 support where the upward firing speakers try to bounce some sounds off the ceiling. Sonos only supports 2.4GHz (no 5GHz support at all) so in a congested area network degradation is a big issue. Codec support is limited as well. For example…
Whether it's TVs, cameras, surround sound systems, we reached a point of diminishing returns by cramming in more pixels or speakers. At that point, you're competing on factors like convenience. There will still be markets for 7.1+ surround sound or DSLR cameras, but they're smaller now.