What is the essential difference between Debussy's composition and traditional composition?

Debussy is the founder of Impressionism, but he himself does not admit that he is Impressionist.

Because he thinks music is a free art, he can't shut it in the room and become an academic art.

Different from the tradition, for example, Petias and Midsan, a work that others think is an opera but he thinks is a lyric drama, the vague meanings of lyrics and images are matched with the strange and restrained colors of music, and the music part of the joint drama occupies a dominant position in the continuous orchestral background. After Debussy, no one can write such a work with rich orchestral tones.

The difference between his music and tradition is that he does not try to tell a story and some specific emotions, but creates an "emotion" or atmosphere that conforms to the theme or title of his work.