Did you know that Jesus himself only uses the word "church" twice (both times in Matthew)? That's it.
The first time is in Matthew 16:18--"And I tell you that you are Peter, and on this rock I will build my church, and the gates of death will not overcome it." The "rock" Jesus will build his church upon is the foundational confession made by Peter that Jesus is, in fact, the Messiah, the son of the living God.
The second time Jesus uses the word "church" is in Matthew 18:17--"If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector." What is Jesus talking about it?
If we read the entire chapter of Matthew 18, we see that Jesus is concerned about relationships and reconciliation. When he uses the word "church" here, he is not discussing church organization or structure, leadership, or acts of worship. For Jesus, "church" simply was not something you do on Sunday, but was a way of life you lived all the time.
He concentrates on reconciliation because he knows how hard it is to maintain relationships with others. It is easier to simply ignore or avoid those on Sunday whom we don't like or have a problem with rather than humble ourselves and seek reconciliation with them.
But to follow Jesus, we must actively seek to be reconciled to each other. To be reconciled with each other, we must approach them with humility, care enough for them to go after them when they've been offended (or caused offense), and freely forgive, just as we've been forgiven.