Lutheranism desire to maintain whatever best contributes to good order, peace, and harmony in the church.
The Bible reveals the Sacraments to be the means with which God distributes his grace and promises. God attaches his word of promise to the element of the Sacrament.
The Latin word "Sacrament" means mystery. God's gifts are given in God's mysterious ways. He offers, gives, and seals the forgiveness of sins earned by Jesus Christ.
In the wide sense, the visible church includes all who are seen together around the sacred Word of God and the Sacraments. This, of course, includes hypocrites and evil persons who mingle with believers, including (it is sad to say) some pastors and leaders of the church organization.
In the narrow sense, the invisible church includes all who genuinely have faith in Christ, an aspect of church that cannot be seen. Fellowship around, in, and through the Word and Sacraments define unity in the faith.