There are some good AAR's and tutorials written by players in various places on the web. Making those more visible would help players who have a hard time understanding what's going on, what to do, and what's fun about the game.
If that and the demo don't work, it's probably just not a style of game they'll like.
I was completely hooked by the Dominions I demo - my main anticipation buying the full game was wanting to get Black Plate infantry and Guardians for my Ulm game!
PvK