Interesting post, Maximus. Good points.
Having been in the 1st Mar Bde at the time, I can testify that what you say is true and that the Bde and later the Div did everything it was supposed to do. I can also say it was not easy; it got done but it was tough and there were excess casualties due to all the factors you cite.
There were two differences then and now which may or may not be significant, only time will tell. The first is that the Officers and NCOs of the Div virtually all were combat experienced in WW II and a large number had prior 'Banana War' experience and all that experience was generally in their nominal field of expertise. The second is that there was a difference in general attitude with respect to acceptance of what the fates wrought then as opposed to now, I believe.
It is pretty well proven that COIN efforts enhance the skill of individual Infantrymen and are neutral to mildly detrimental to the skills of those in the other Combat Arms.
Given all three factors, I think that skill deterioration is a big concern -- but I agree with you that the Troops will make it work regardless under most circumstances.
Not to take away from the concern
But can someone tell me what the likelihood of Full out and out Ground Arty component being a mainstay in the future. If the USAF gets the 22's and others then when comparing ground arty in relation to Air or Naval Arty which are the more likely to be used in largess. Isn't it a little harder for an enemy to take out supporting assets that are in the air or the ocean than on the ground.
Pound for pound what is the tradeoff between these and is it even something to be considered or can our forces not accomplish the missions without 155's on the ground.