In order to better understand the issue, we ought to take into account at least two biases prevalent in the developed world:
(1) Professionals are paid well enough to afford decent to excellent audio gear.
(2) Negative reviews of audio gear are suppressed, either culturally or through money factors.
For me, reviews on Russian site
https://carmus.ru were illuminating. The site's primary mission is sharing knowledge among car audio systems installers. The reviews are quite different from the ones you'd find in English-language sources:
(A) Their customers are constantly pushing them to install dirt-cheap gear, some of which - usually made by lower-tier Chinese manufactures - isn't even available in the US.
(B) Slavic cultures tolerate criticism better than the Western ones. If a piece of gear measures like sh*t and sounds like one, the reviewers find it acceptable to just say so.
(C) They disassemble the gear, and list the model numbers of critical active components. They also sometimes opine on the parameters dispersion of the passive components they find inside the box.
After reading couple of dozen reviews of car amplifiers - some of them rated as exceptionally clean-sounding, some of the them as OK, and some of them as having unbearable glare - I formed an opinion that the sensation of glare could in many cases be associated with intermodulation distortion, measured via protocols not widely used in the West.
For instance, look at
https://carmus.ru/content/236. This is a review of a budget A/B car amplifier, which was found to sound "harsh". The spectrograms showing intermodulation distortions evoked by 5+6 KHz and 10+11KHz signals are revealing.
The 5+6 KHz spectrogram shows about 20 spikes in the uppermost octave, some of them as high as -45 db.
Integrated over the corresponding critical band, they may produce enough power to be heard.
Compare this to a high-end amp, reportedly with a huge fan following:
https://carmus.ru/content/234. The 5+6 KHz spectrogram shows only about 10 spikes in the uppermost octave, none of them higher than -80 db. The subjective evaluation section describes its sound as "airy" and "nuanced".
Also note the Linearity & Distortion Analysis graphs. I rarely see this in the Western press. Some of them are quite embarrassing to the amps manufacturers. Take this one, for instance:
https://carmus.ru/content/191. It turns out that at lower signal levels its THD can be as high as 0.4%, a manifestation of the infamous "first watt problem".
Now look at this inexpensive Class D amplifier:
https://carmus.ru/content/313. Not only its THD can be as high as 0.5%, but the dependency between the signal level and THD isn't even smooth. On some types of music material, with narrow dynamic range, it won't matter much. On others it may be heard as annoyingly unpredictable timbral shifts induced by signal level changes.
I don't have similar measurements of budget DACs handy, yet some of them may well exhibit similar characteristics, at least that's what I subjectively heard over the years. Most likely, this happens because of not enough attention paid to the analog output stages design, production, and quality control. The DAC chips may have something to do with this as well, yet my personal experience doesn't corroborate this.
For instance, some of Mackie professional gear uses inexpensive DAC chips dismissed by the audiophile press. However, to my ears, and to the ears of thousands of music professionals, they are transparent. On the other hand, sometimes I would get excited by a new DAC chip, only to find out that a certain presumably audiophile DAC, one of the first to the market with this chip, sounds not so good, and is not worth keeping.
