What is the problem with mainline Christian denominations?

Self definition, or the lack of it, is the problem with mainline Christian denominations. By self definition we mean "do we know who we are?" Many folks who attend worship every week are not sure why they keep coming to church. These folks are cultural Christians as identified by Gabe Lyons in his book "The Next Christians." Perhaps the local church feels familiar and comfortable like a favorite pillow or winter coat. The deeper meaning of the gospel, the urgency of our task, is lost as we "play church" rather than "be the church" (Cecil Williams). We are Christians. We are followers of Jesus Christ. This needs to be shared with passion to the whole world. People find themselves in some dark places, looking for meaning in a world that simply skims the surface of life. It is good to be "nice" and thoughtful, and practice random acts of kindness but that is not the Christian faith. We are Christians. How can we invite persons to a transforming church when we are not sure who we are and not fully commited to being all that Jesus calls us to be? Thoughts? ideas?