This criticism is usually made by people who have made a sincere effort to listen to an unfamiliar form of music, and who believe they are making an objective judgment about the music itself. It seems more likely to me that what they are doing is revealing a fact about the structure of musical ignorance. E veryone knows that music expresses itself by varying certain qualities of sound in certain patterns, such as melody, harmony, rhythm, and tone color. What is not so well recognized is that every form of music is necessarily simple within certain qualities, so that it can be complex within other qualities. This is why a conductor, who plays no instrument himself, is needed to control those two qualities.
Most Baroque music has comparatively little variations in dynamics or tempo.
It was only when he learned the intricacies of counterpoint that he was able to appreciate the subtle beauty of Bach's interlocking melodies. No, for certain kinds of variations inevitably cancel each other out. The tempo variations of romantic symphonies make it impossible to do complex rhythms, because it is impossible to hear a rhythm going against the beat unless there is a steady beat to provide a foundation. It is also impossible to play jazz chords through a distorting rock and roll guitar amplifier, because the amplifier adds harmonics that clash with jazz harmonies. E very culture's music thus makes certain choices about what to vary and what to hold constant.