Why the Mainline is dying?

In the most recent book I have begun to undertake, Almost Christian (you can see the book cover and link to the right of this post in the "goodreads" box), the author Kenda Creasy Dean makes several arguments about the current state of affairs in the Church.  While this entry is not a critique about the entire book (of which I highly recommend to anyone who wants to understand not the future but the current state of the Church), I did want to share one aspect of the book which connected with me deeply.

The argument is that there are some youth who are very devoted to the Church and the mission and ministry of the Christian Way (about 8%) and there are four characteristics these youth possess that other youth do not in regards to the Church:
1.     A Creed to believe 
2.     A Community to belong
3.     A Call to live out
4.     A Hope to hold onto
Of those youth in this category there is a higher proportion of LDS (Mormon) church members than any other denomination.  The next most represented denomination in this "devoted" category are members of Evangelical Non-Denoms.  The Mainline is the next represented group, with Catholics near the bottom of the list.  
As I reflect on my local community of faith, we take a lot of pride in fostering the second of the four characteristics.  We use words like 'family', 'connect', 'belong', 'fellowship' and even 'get together' a lot in our faith community.  While not nearly as dominate, we also take some pride in the first characteristic of the four and put a lot of effort in making sure we are teaching 'good theology' striving to remain 'open' to different theological perspectives, and using gender neutral language for God as best as we can.

However, these third and forth characteristics are hidden at best in my faith community.  I do not believe this is intentional at all.  We do not disregard Call/Vocation or Hope/Future but these seem to take a backseat to our Creed/Teachings and Community/Family emphasis.  And it I wonder if this imbalance actually firmly locates my faith community in the past/present unable to advance into the future and vision?

It seems to me the ability to call people to live a certain way or the ability to share a certain hope for the future is understood as “divisive” by some who want to foster a community and a common creed.  It is difficult for some to see how we can be “divisive” and also maintain a community and a unified creed.  So these individuals,, for the sake of Community and Creed, do not spend much time on potentially “divisive” issues of Call and Future.

Could this be one of the reasons the Mainline Church is on the decline?  We are living in the past and present out of a potentially “divisive” future?