Alister McGrath, writing in his book, Christian Theology: An Introduction, summarizes Luther – and Reformation thought – with regard to the institution of the church by saying (p.397):
An episcopally ordained ministry is therefore not necessary to safeguard the existence of the church, whereas the preaching of the gospel is essential to the identity of that church. [Quoting Luther:] “Where the word is, there is faith; and where faith is, there is the true church.” The visible church is constituted by the preaching of the Word of God: no human assembly may claim to be the “church of God” unless it is founded on this gospel. It is more important to preach the same gospel as the apostles than to be a member of an institution which is historically derived from them [emphasis mine].
Let that roll around your mind for a while.
