That's a very difficult question to answer, as there are many variables involved -- the room, the listener's hearing, psychoacoustics, placement, perceived reputation of the maker, ect, ect -- but I will hazard a very general rule. If that speaker distorts below 85 dB, most people would walk away. Just talking about it, I can't emphasize enough the APPEARANCE of the speaker : if that speaker looks good, a person's brain is going to think it sounds good. Remember, Bose made the 901 for over 25 years. And Zu Audio wouldn't be in business.
I would note that in controlled blind circumstances with fast switching, all the difficulties you mention fall away.
In sighted circumstances... in other words normal circumstances, your ability to discriminate is lower. There's no getting around that. And I think most people conflate speaker sound with that of the music and everything else you mention, which is like trying to assess a giant nebulous glob. So they don't, rightly. The only place where that changes is when they are trying to buy speakers. And there it becomes extremely difficult despite the buyer using whatever critical ability they have. Marketing accounts for almost all available information. You don't have much to lean on, and you can't really go to a speaker store for the most part to try anymore because of online shopping. Cue the rise of reviewers.
If we think back to the very realistic-sounding, for the time, single driver radios... or megaphones for PA. Or someone shouting from another room. Seems like we are almost always in circumstances where sound sort of sucks and we have to make do with whatever sound cues are available. That's a passive position, and it doesn't lend itself to imagining how sound could or should be different or better.... unless the sound is abysmal and the message is obscured. Then you yell at the other person to come closer, or revolt against the very muffled dialogue of the theatrical version of Tenet. Those are obvious examples, while assessing a speaker for its sound is in no way obvious.
Take the 901. It is a speaker engineered to take advantage of walls and early reflections. How are you supposed to assess that or figure out what's wrong? Or take any normal speaker and read the impossible comments about more or less bass, boominess or limpness by people who don't understand room acoustics. They think they are assessing the speaker when they are assessing the sound at that point in the room, which is moreover dominated by the room.
I once had a guest comment on my amazing system at home. I later sat on the same spot on the couch, which was off to the side of the firing line of the speakers, and leaned to rest on the couch's arm like she did. Her head was in a room mode. Just huge bass at 60-80Hz at that one spot, way more than anywhere else in the typical listening positions of the room. In a way, her compliment made me suspicious enough to investigate. I knew it was wrong because I have years of striving for neutral sound in my head. She didn't because she enjoyed the oomph. It's hard to make the right distinctions and ask the right questions of yourself unless you are somehow motivated to do so.