My first contact with a staff was in the early 50s -- and the staffs I saw were notable for getting out and doing things-- gathering information and spreading the word.

As I later 'progressed' (after fighting and avoiding it as long as humanly possible) to a staff it just happened to be about the time that staff sizes and ranks were increased and more information became available for use -- both those things due to a variety of factors.

At the tail end of my nominal career, I was on a large staff that truly had access to more information than it could digest but in visits downstream, I noticed the same thing at all levels; the staffs had become a filter and the ability to do something truly directed at mission accomplishment was an exception to the rule of constant filtering.

Look at that as it goes upstream; trying to do something for a Bn mission impacts the Bde staff as it becomes something to filter; at Div it becomes just another item of dust...

Thus your point:
"...This transformation continues and is not yet complete, but I believe that staffs twenty years from now will look superficially the same but will in fact function quite differently."
is I'm sure correct and one has to wonder if the staff malaise factor which is quite real and an at least mildly adverse impactor on individual retention and on unit performance will be addressed in the process of that development...