To whatever degree an otherwise competently designed and implemented speaker cable, interconnect or power amplifier alters the sound in a perceivable way, it is due to frequency response differences. These have always been fairly easily correctable with EQ, but it may be true that it is a relatively recent trend that well heeled audiophiles are accepting of this EQ in the form of advanced room correction - a break from the old "straight wire with gain" school of thought.
For example, any high frequency rolloff of your citadel monoblocks was a linear phenomenon and could be compensated with suitable measurement and eq. Any cable causing high frequency or low frequency rolloff can similarly be compensated.
The caveat of competently designed and implemented is because of course a trash amplifier can be built (and some indeed are sold) with distortion products into the audible range. I consider these broken, since it isn't expensive to move into the range of inaudibility. And of course you can choose an amplifier underpowered for your speakers in your room with your desired listening level, and drive it into clipping or worse. But that isn't competently implemented.