Boulez may have been the best all around conductor of 20th century music.
But how did he conduct Bach, Handel, Haydn Mozart, Beethoven, Schubert, Schumann, Mendelssohn, Brahms?
He disliked Mendelssohn and Brahms and never conducted them. When he was hired by NY Phil he said “I hate Tchaikovsky and will not conduct him.”. He also hated Dvorak, Strauss and all 19th century Italian opera.