It's the speakers.
The ultra high end speakers have like 17 drivers in them and not even a 1000w mega amp can drive them properly. Imagine trying to design a coherent crossover for such a multi driver array, with many of those drivers housed in 4-5 different separated cabinets.
This is why all they excel in is the bass and large orchestra, the smaller scale stuff and music at low volumes sounds terrible.
The other issue is lack of positioning. A movement of cm, even a few mm, can dial in a speaker drastically. These top of the line ultra speakers all weight at least 200kg, sometimes 400-500 kg each. They just get plonked down and that's it. Yes they calculate the position beforehand, but this can never account for the real world room conditions, and its impossible to do trial and error positioning with such heavy speakers.