Why did the bishops start the homily discussion with the assembly? More reasoning:
[5] Contemporary ecclesiology provides a second and even more fundamental reason for beginning with the assembly rather than with the preacher or the homily. The Dogmatic Constitution on the Church (Lumen Gentium) describes the church as the mystery of God’s saving will, given concrete historical expression in the people with whom he has entered into a covenant. This church is the visible sacrament of the saving unity to which God calls all people. “Established by Christ as a fellowship of life, charity, and truth, the church is also used by Him as an instrument for the redemption of all, and is sent forth into the whole world as the light of the world and the salt of the earth” (#9). The church, therefore, is first and foremost a gathering of those whom the Lord has called into a covenant of peace with himself. In this gathering, as in every other, offices and ministries are necessary, but secondary. The primary reality is Christ in the assembly, the People of God.
Lumen Gentium indeed says this, and it begins its discussion on the Church with the “people of God.” The Church is first and foremost a manifestation of Christ’s saving grace in baptism. Other qualities, aspects, and sacraments are indeed necessary, but of necessity, they spring from baptism.
[6] This renewed understanding of the church is gradually becoming consciously present in the words and actions of the Catholic people. By means of their involvement in diocesan and parish organizations, their sharing in various forms of ministry, and their active participation in the liturgy, they are beginning to experience what it means to say that the people are the church and the church are people.
Written in the early eighties, I think this assessment is mostly accurate. It suggests the bishops knew liturgical and ecclesiological reform was still in its beginning stages, not a finished product, and still needful of much work. Hence this document.
Comments?
(All texts from Fulfilled in Your Hearing are copyright © 1982 USCCB. All rights reserved. Used with permission.)
Catholic Sensibility 
A clarification for those who don’t want to bother reading LG again: LG says some of this, but far from all of it. Much of this is a particular interpretation in the context of the purpose of this document.
1> What in this is not repeating LG?
2> Does this particular interpretation have more authority since it comes from our bishops, the official interpreters? (assuming you are from the US; if not, the answer might be different)