One somewhat odd feature I find on older courses that have been lengthened is that often the back tees are set back in such a way that on a downhill tee shot the fairway is not visible from the tee, you just see the nearer tee boxes.
My home course has several tees like this, and even though I've played the course many times and there's no real blindness there for me, I still find that when I have occasion to play the next set up I feel much more comfortable on the tee and have greater success hitting the fairway.
Might this not be an underrated source of additional difficulty on these older courses, versus newer courses that had the tips designed in from the beginning -- typically sitting on a higher plateau and more often than not offering the best fairway view of all?