Capt, I'm going to have to disagree with you to some extent here. While you're certainly correct that in many such fights your artillery is going to be dragged in many directions, I don't think that's enough rationale to make this feature unrealistic. If an artillery unit was given to your direct support, or you are the brigade or even possibly division main effort, there is no reason in the world why you couldn't have artillery missions waiting for a specific go word, especially on the attack. But even on the defense, having an Final Protective Fires mission ready and waiting to go without having to have it all spotted or making a wild guess with how long it'd take for the TRP to call in would be a serious jump in capability. As it stands, FPF can't even really be modeled in CM in a useful way, and one can't go on to pre-registered attacks on enemy depth following an initial mission without extensive TRPs covering practically the entire map.
tl;dr, The fact that they often might not be realistic doesn't completely obviate the times that they are completely realistic.