Taruskin wants to maintain simultaneously that Western music is a dying tradition and that historians need to stop holding 19th century composers in a place beyond criticism. But the composers whom he would choose to dismiss as the exceptions to the trend of dying Western art music—Reich primary among them—are exactly those composers who have chosen to insist that 18th and 19th century composers are not worth imitating and the composers of the Medieval period and the 20th century are. These composers have the boldness to assert what no musicologist ever would. Perhaps Taruskin himself is still prey to an unseen idolatry of the common practice period: his historiography still blinds him to the significance of the people who are actually bold enough to question the common practice, the composers.
Musicologists have a vested interest in dismissing Steve Reich because his music is an unvarnished rejection of the ideals of autonomous art music created in the 18th century, and that rejection would seem to threaten some of the most basic assumptions that grant them tenure and position in the academy.