At this point in the debate, a defender of the traditional Lutheran heritage of worship will have many places to turn in the Confessions to combat this notion - to show that acceptable "diversity" in Lutheran worship never included tossing out the Western Mass, doing away with reverence, dividing congregations by age group or preferred musical taste, etc. And that is an important argument to make.
But there is also this: history. The fact is, the men who wrote and signed the Formula of Concord all lived in churches where such decisions were most certainly not made at the parish level. The bishops, called in some places superintendents, sometimes working with consistories and even Christian princes put forth ecclesiastical law regarding worship that was binding on the local parish. Read all about it.
I am not myself a scholar of the Kirchenordnungen, so I'll leave it to others to supply good bibliography and commentary. I only make the plea that we give attention to this important fact that stares us right in the face: the men who wrote and signed the Confessions had binding church law regarding worship. Maybe that's not such a bad thing after all. . .