Actually, the film (in my estimation) is a comment on the indomitability of the human spirit...
McMurphy finds himself in a particular situation over which he has little control... but battles his nemsis anyway.
I particularly like the scene where he infuses "Chief" with a sence of pride... during the basketball game.
Next to this, the scene where McMurphy describes how he would break out of the institution by ripping ut the huge handwashing sink and throwing it through a window, attempts it, and of course fails, but "Chief" is quietly observing all this in the background. This achievement is repeated at the end of the film with Chief actually accomplishing this feat all the time with haunting Native American music playing in the background. Although ancient, I found it entirely moving and found revelance in McMurphy's triumph over Nurse Ratched, through Will Sampson's portaryal of
"Chief" ("Mmmm... Juicy Fruit" was a pivotal line in the entire movie)
Although more complex and at tiems, difficult to follow, Ken Kesey's book was also a searing commentary on our society.