True, you should not detail everything to the same standard (foreground/background), but you should AA everything I think. Not AAing part of it and going "because of focal point" is a pretty bad argument. If you want a good focal point you plan the drawing out first and make a good composition. You can do all kinda of stuff, like having more intense colours around the sword, having that area be brighter, having certain lines lead there or whatnot. Just not AAing the surroundings will look pretty poop I think.