Plain fact is that I'm slower than I used to be. Also not as thin. Or dark haired. I could train harder and harder still, but would still be slower than that younger me of some years ago.
However...........I have perhaps more fun these days now that I near 60. I tend to actually look up and around me more often, stop at scenic overlooks, etc. I don't see other riders as "the enemy" to be caught and passed. Not that I wouldn't like to blaze up the road, but it just doesn't seem so critically important these days.
If you need an analogy....I consider myself a sport touring bike these days, rather than a racer.