We all know the modern complaint: movie sound sucks now unless you have a high-end sound system. Frantically turning down the volume after turning it up to hear the dialogue only to need to turn it up again can be frustrating. Now, this doesn’t solve the underlying problem, but why not have a “Volume A” and “Volume B” you can easily set and toggle between with the simple press of a button?
Also a self reply to add that I don’t use the downmix because I got lucky and in addition to free old PC hardware which most people in the USA at least can also get free or cheap if you are creative with old business hardware. The addition is I got an AV Receiver just barely new enough to support HDMI so I do have the full range of channels on very cheap speakers.
Having used Kodi elsewhere the downmix seems to work just fine and a lot of current and still fairly cheap sound bars can interpret surround mixes directly.