Many former great players still alive and in their late 60s and into their 70s. As a 68 year old in excellent shape who still competes in tournaments at times, let me give you some perspective :
eyesight should not be an issue as much today as modern technology can make almost anyone 20/20 at any age if they desire ( cataracts are a factor though, as they must be diagnosed to be treated);
any degree of arthritis in knees, back, hips, shoulders, hands will usually increase to varying degrees with age;
physical strength, unless they are able or willing to be in a gym with weights a few days a week will diminish,
longer term stamina and focus abilities will also diminish with age
weight gain is difficult to stave off with age
They might be OK if they stayed in a winner's bracket to the very end of a tournament, but going into the losers bracket early will test the stamina of anyone 50+ in age - just too long a grind from that point to the end.
Some may disagree, but the proliferation now of Diamond pro cut pockets in most pro tournaments may be the nail in the coffin for older players of any speed who spent most of their life competing on 4 3/4 to 5 inch pockets on tables that did not demand perfect strokes. Just look at tournament videos from 1980 to 2000 and the table pocket size was much larger and the speed off the rails was easier to manage without a perfect stroke.
