Let's say that the following is assumed:
Significant harmonic distortion increases speech intelligibility, improves definition of time references in the sound image. On the other hand gross dispersion errors create disturbances and an unbalanced sound energy that degrade speech intelligibility, smear time references in time, and mask decay. Loudspeakers with limited dynamic characteristics also mask the same factors. No EQ is used in the two scenarios.
Scenario 1:
You build a setup with an amplifier that distorts well below the limit for audible distortion. You have control over the speaker directivity, which is also limited. The speakers have good dynamics and very low distortion. You also have good control over the acoustics.
Result:
It sounds amazingly good and a large majority of those who hear the set-up will easily agree that this sounds fantastic. This is also, what you find in the control rooms of the very best studios around the world.
Scenario 2:
You build a set-up with speakers that struggle with an untidy dispersion pattern. If placed close to various surfaces in the room you get a series of unfortunate reflections that are far from linear in frequency. This reflection energy constitutes a much greater proportion of the total sound energy than in the 1. scenario, and the spectrum sound distribution for the reflected sound is of an unfriendly nature with a focus on frequencies from 2-5kHz. Frequencies above 5kHz, where a significant part of the time information is located, are underrepresented in the total energy, and the time domain generally does not look good.
The ears do not hear weak sounds immediately after a strong sound. These weaker sounds must have a certain duration in order to be perceived them. This is expressed through the Gaussian masking curve. So loudspeakers with limited dynamic properties and that spread a lot of energy over time and create a non-harmonic reverberation image that lies far outside the Gaussian masking curve. You connect an amplifier with quite a lot of harmonic distortion in the setup.
Result:
You get more spectrum information because of the amplifier, and it becomes easier to perceive time information. It also becomes easier to hear reverberation. The sound is experienced as significantly more natural than if you put a neutral amplifier into the same setup. Most people would also identify this as a good sounding set-up, but here there would be far more caveats. Experienced listeners, preferably those who work in a studio on a daily basis, will think that this sounds appealing, but not right. Recordings sound more similar, a bit like always using the same spices in food. It does not have the same positive effect on all raw materials, even if the food would be experienced as tame without spices.
What if we switch?
What if we take the amplifier from scenario 2 and insert it into setup 1? Are we getting better sound? Are we getting more appealing sound? No, believe me, I've tried this. When the basic things are in place, this is like smearing your whole body in perfume before going on a date. No one finds it appealing. You will probably immediately react to noise, distortion that masks the space in the sound, dynamics that cannot be released, bass that seems grounded in a duffel bag, treble that feels intrusive and at the same time a bit dull. Some of the effects are subtle, but nothing will turn out in a positive way.
This is not an argument that one amplifier is better than the other, unless one establishes a definition. Still, there is an argument to the contrary. It is because the neutral amplifier will also make the set-up in scenario 2 sound subjectively clearly worse. So what's the point?
It's as simple as getting the very best sound with a neutral amplifier, provided you also have control over everything else. In many cases, you will get a better sound with the amplifier from scenario 2, but you will still not reach the sound quality level in scenario 1.
Therefore, it would be wrong to say that the amplifier from scenario 2 sounds more natural than the amplifier from scenario 1. One could go so far as to say that it is the other way around, that the amplifier from scenario 1 sounds more natural than the amplifier from scenario 2, but with the fact that in many setups this is simply not true, that argument is also a "long shot".
In my book, there is no doubt as to which is the overall best amplifier, but at the same time I have no problems either, understanding why the amplifier from scenario 2 plays a legitimate role in the hi-fi market. I can also enjoy music over such a set up. However, for me, this hobby is also about looking even further and dig deeper. Fortunately, the hobby does not stop me from enjoying music along the way.