I suppose you may have read Pope Francis' words. I think it means that Pope Francis just wants Christians to be active participants in church rather than loafing around and doing nothing. Inactive, non-practicing Christians are no more useful than the "fluffy bunnies" of neo-pagan religions, bordering on being false believers and utter hypocrites. One may "belong to God" by receiving the invitation of salvation, but that's easy. One must participate in the party in order to belong fully to God.
Pope Francis explains his rhetoric by alluding to the Parable of the Great Banquet. Salvation is being compared to a great delicious feast that God holds for all his invited guests. If his invited guests (people who self-identify as Christians) do not come, then God will think of them as being ungrateful and skips them; God will instead look for more grateful guests by gathering believers on the streets. Additionally, it is known that Roman Catholics baptize infants. Using the same analogy, these Catholics are put on the guest list by their parents who expect them to worship God and presumably live a holy life. Well, these Catholics claim to be Catholics but aren't real Catholics because they do not follow God or the church, or even live a moral life. Therefore, non-practicing Catholics aren't really saved at all.*
*It is NOT to say or give the impression that nonreligious people cannot ever be moral. This is just about a particular group of "Christians" that identify themselves as Christians but really do not do Christian things like praying, worshiping, attending services regularly, or at least implementing Christ's teachings in everyday life.