While I do agree that Arma 2 obviously suffered from usability issues which turned a load of folk away, I do not agree that there were no "enjoyable" missions. I tend to play with the United Operations community, and on their servers I will be an air cavalry soldier raiding a VC outpost in vietnam (lingor), or a British soldier being ambushed by the IRA. In my own missions I have created, my TvT (PvP) missions feature: Government forces try to stop a cartel drug convoy reaching its destination, a rogue russian unit tries to assassinate the US President, PMC, British and Insurgent forces fight to extract an HVT from Zargabad, and more! (Those mentioned feature 70-80+ players).
What I want to see is the gap that currently separates those who just buy the game, join vanilla servers and get bored and those communities and servers that provide interesting missions closed. This should happen with the modding support, but more changes will be needed as well, I look forward to testing and suggesting in the alpha.