Formal musical composition in the tradition of Bach, Mozart, Beethoven, Schubert, Mendelssohn, and Dvorak (to mention only a representative selection from a vast array) took a turn for the worse in the early 1900s. “Modern” music as it was then and has remained, consists of the following styles:
Gloomy music for a gloomy day/event/epoch — sometimes vocalized for extra dreariness.
Hyper-caffeinated cacophony for noise addicts.
Ponderous musical platitudes, piled high and at great length.
Random noise and random silence, in various proportions.
Throw in dissonance, atonality, lack of rhythm — and just plain non-musicality — and you’ve got “modern” music.