Well honestly, I'm against winning on anything but flag captures. Of course I know with the current system there's no way it can change. But in future reference you should only be able to get 1 point each flag capture and the limit of flag captures would of course then be set with the server. You know, the standard pick-any-commercial-game-with-ctf-option game.
But other than that, I agree that defenders too should be able to win, but flag captures would give lot more points of course, thus ending the game faster.