It's important to note that doctrine and policy are not being changed, but the tone and emphasis are being changed. As one Vatican spokesperson I heard discussing the conference noted, the church has always stated that every person is a child of God, but now "that's the first thing we will say."
(It should also be noted that this is pretty much in keeping with Francis's M.O. up to this point. He hasn't actually changed any Catholic doctrine; he's just changed the conversation to emphasize portions of doctrine that have often been lost in the noise. [God's love for all people, the need to act with humility, presenting an attitude of servanthood to the world, etc.])
In the days since the document was released, there has been some strong pushback and attempts to clarify what is being said, especially from more traditional bishops. At this point, it's not clear what the final word or actions may be, but I'm still excited to see Francis making the effort to have the conversation.
I don't agree with the Catholic Church on everything that constitutes a "sin," but if we spend too much time telling those outside the church about sin, then that's all they hear and any word of welcome or grace (the most important part of the message) sounds false. The message shifts to one of "you need to get your life together before you're welcome in a church" and starts to include "faults" that go beyond sin like doubts or depression. Where else in our society do we have this kind of backwards expectation? We don't say, "get yourself healthy before you go to the hospital" or "become an expert in your preferred field of study before you apply for college."
This whole topic deserves more time and nuance than I'm going to give it in this blog, but please allow me to oversimplify by saying: the message from the church should always emphasize that sin (however we define it), doubts, or personal shortcomings should never stand in the way of being welcomed in church because we are all -- Christian and non-Christian -- imperfect and we are all -- Christian and non-Christian -- still loved desperately by God.
We don't need to get our life together to come to church because being in church--or better put, being in regular relationship with God and God's community--is how we are meant to get our life together. Francis has been showing through his words and actions that if we want to be effective at changing lives, it helps to first have a genuine relationship with a person. Jesus himself demonstrated this in his ministry (see John 8 as an example). If we start with loving people as they are and seek to serve rather than preach, I think we're far more likely to see the growth of God in them (and ourselves) that we hope for.
“Change has been; change will be.” -Collective Soul, “Reunion”