The church only lives up to its mission in that others are placed more important than itself. Those others are other believers in the church and those outside the church in the world.
To the degree that the church turns inward and the church becomes about oneself or simply those within the church the church has lost its mission. The early church spread quickly because it understood that Christianity is something to be shared.
The more the church focuses on itself and its survival the poorer and less likely to survive it is. The radical thing about the gospel is that God accepts everyone and it is through spreading the gospel that it has power.
Often today churches sit and hope that people will enter the confines of the church. Maybe they do one small event in the community each year. But often the church faces inward and the inward faced church is not healthy. It does not fully grasp the gospel.
Sometimes the inward facing is because of a desire for purity. If we pull literally every sinner into the church then it will be hard to maintain the purity of the church seems to be the objection. It is of course one of the main objections Jesus' enemies had against his ministry.
You see we often assume that the people in the church are meant to be there. Or that certain people outside the church are better prospects to be pulled into the church than others. Our assumptions are almost never helpful and often wrong.
It is an interesting phenomenon that often God calls the most sinful people into the church. It plays out repeatedly through scripture and church history. I believe the point is that some people in the height of their folly understand that they are broken.
They may not have an answer but they often know that they are on the wrong track. You see that the broken sinner with little hope who knows they are on the wrong track may be a better candidate to enter the kingdom of heaven than the wealthy non believer next door who seems to have their life together.
Ultimately we cannot know why they will enter the kingdom of heaven but assuming the quality of prospects is folly. And the church should always have an outward eye toward the world.