Aging can be cruel. I have noticed that those who were athletic and were reasonable with their lifestyle seem to fair a bit better, such as they still have respectable distance, atleast till they reach 75, can still post scores close to what they did 20 years ago. Of course there are the one off, arthritis, worn out joint that can have a negative impact.
Having to deal with osteoarthritis in the hips and a L4/L5/S1/S2 issues for the past 12 years, has been somewhat inconvenient but ar 70 I dont feel old, just some restrictions.
But as some have noted, Senior Tees makes the game more of old. For me it is my short game, without it, I couldn't 90, maybe 100. One other skill I developed has been how to play the game, how to create scoring
opportunities with my limited skills, how minimizes lost strokes to par.
With age comes wisdom, sometimes.
Side note, no real medical issues or pain then on 1 Jan 2000 I was admitted to the E/R, next day I left with a pacemaker. 30 days later, I retired.