Author Implication on Nineteenth Century Art

One of the attributes that distinguishes great artists is their mastery of technique. Their superior ability is recognized by other artists, who admire and emulate their work. This is not to say that facility alone is sufficient. Nineteenth-century painters and sculptors were among the most proficient artists in history—as well as the dullest. Even the most painstaking piece of craft does not deserve to be called a work of art unless it involves a leap of the imagination.

The author implies that the works of the "nineteenth-century painters and sculptors" are