Christianity Today ran an interesting article recently: Three Views: How Can Churches Reach Nominal Believers Before They Become 'Nones'?

In the article, Drew Dyck argues we need to stop pussy-footing around and instead challenge nominal believers:

There's still a place for this kind of frank conversation. Often, loving nominal Christians means presenting them with the hard truth of what it means to follow Jesus. Seeing their true spiritual status may be a necessary step toward faith.

Kenda Creasy Dean thinks showing better biblical hospitality to nominal believers is the answer:

When nominally religious people experience the church as a community of people who embrace first and preach later, who celebrate life in those given up for dead, who err on the side of grace in matters of doctrine and politics so that no one, ever, must sit on the margins—we're far less likely to lose people around the edges.

Eddie Gibbs is convinced that too many churches lack authentic, consistent, relational discipleship:

The church members most at risk of becoming nominal avoid close personal relationships, which provide the context for encouragement, accountability, and ministry opportunities. These are bored consumers who "go missing without being missed." At the other extreme, Christians who are burned out may also be at risk. It is not unusual for church leaders who are worn out by ministry demands to move elsewhere and drop out entirely.
Also, unfortunately, biblical illiteracy is disturbingly high among many churchgoers. This creates vulnerability to the prevailing secular culture.

All three have valid perspectives. All three are right. The whole article is worth reading.