[dragonwriter]

> But I still don't see why the answer is to pray rather than exhort people to do something about it.

Asking people to pray is asking them to do something about it.

Not just in the trivial sense that prayer is an action (though that too), or that the specific prayer is asking God to do something (though, again, that too), but more deeply in the sense that prayer is, in Catholic thought, not a onidirectional communication but a dialogue, and praying for an intention is the beginning of discernment of what, if anything, God wants the praying person to do to serve others and make God’s will manifest in the area prayed for.

As for why he isn't exhorting more specific action, that's not what the venue of this call (the Worldwide Prayer Network) is for. The issues raised in that venue are often ones on which the Pope advocates more specific responses in other venues, though.