Erik, perhaps it is a little bit like macular degeneration. Your vision has black spot growing, but you don't know about it (until it is too late) because brain is hiding it from us. Before they discovered Transient Intermodulation Distortions (TIM) in 70s they made quite a few horrible SS amps. Internal overshoot of transitions was so bad that output transistors were going into momentary saturation causing tiny gaps in music. Again, brain was compensating but longer listening was very tiring. I have room that has a little bit too much of a slap echo. I bought acoustic panels but am too busy (read: lazy) to put them on the wall. When I listen at lower volume everything is better including imaging. A little bit more volume and sound becomes tiring. I know exactly that this is my problem, but as you said, brain shifts modes, and sometimes we might not have a clue.
We all know that buying gear based on specifications is silly but perhaps we should even pay less attention to sound itself but rather if it makes us feel good.
We all know that buying gear based on specifications is silly but perhaps we should even pay less attention to sound itself but rather if it makes us feel good.