One of Rumsfeld's ideas is apparently to substitute helicopters and missiles for artillery like the Crusader. I read of one battle where this was put to the test as we moved toward Baghdad. Helicopters were sent against an entrenched Iraqi line, but got shot up without dislodging them. Field pieces were eventually brought up to greater effect.... That was a tactical decision made by on scene theater commanders. It's very doubtful that Rumsfeld had anything to do with that.
And those artillery pieces that were brought up to dislodge the enemy, were most likely Palidin howitzers, which the army has thousands in their inventory.
Rumsfeld made a Command decision not to buy Crusader howitzers believing that the 'cost-to-benefit' was not worth it - I agree.
These generals have made specious arguments against Rumsfeld.
The 155-mm M109 series, Self-propelled medium howitzers are highly mobile combat support weapons.
I'm sure it was a tactical decision. But there's no reason to dissociate Rumsfeld from the operation, other than it demonstrates a known problem with his intention of replacing artillery with air power.
Rumsfeld is not the first SecDef to emphasize a cost/benefit ratio. That was precisely what McNamara was known for, along with a goal for "modernization", and it's why some critics see Rumsfeld as McNamara redux.
Modernization isn't always what it's cracked up to be. There was once a decision to eliminate guns from fighter aircraft. After all there would be no more aerial dogfights. Until there were, and we needed guns and Top Gun training. Some generals are certain that in a future fight we will wish we had effective artillery, despite the fact that they won't ever be needed again, just like guns on fighters.