Answer
Meyerbeer's popularity declined in the 20th century due to critical assaults and neglect by opera houses. Critics claimed that his music was old-fashioned and bombastic, and that he lacked the originality and genius of his contemporaries such as Wagner and Verdi. Opera houses also stopped performing his works, as they were seen as too expensive and too demanding for audiences. As a result, Meyerbeer's music became largely forgotten and neglected.