If you divided the group of all NFL QBs in history in half with the most and least conservative groupings with Weed as the most conservative ever and Farve as the least conservative ever, Aikman would be in the conservative half.
If Butler is single covered on a 9 route and has a step, it's not abandoning a conservative approach to throw him the ball. If you throw him the ball when he is double covered then that is abandoning the conservative approach (unless you do what Weed did and just throw is so far past Williams that it was impossible for him or anybody else to catch it).
Throwing to an open receiver in the NFL is not being non-conservative, it's just being an NFL QB.
What Cassel can't do it try to be a hero and start flinging it around into double or triple cover like he thinks he's Brett Farve.
Obviously, if they get significantly behind on the scoreboard then he would need to take more chances; however, to start the game he needs to minimize the risks and give the defense a chance to step up to the plate now that they have all hands on deck. If they don't get significant pressure and rattle Eli with Hardy and Gregory now playing, then the Cowboys have problems beyond this game.