I really think you will miss out, we choose a holiday for the destination and its the safe way to travel. You see so much and do so much they really are great tours..
I started using JY in 2006 I am now 57 age has never been a problem I have been away with people in their 20's or 80's talking to people and hearing their conversations is part of life's rich tapestry, you can be young but be old or old and be young...I worry more about the fitness, I have been out walked by 70 years olds...age is a number, I love being in a mixed age range.
If you have your eye in a tour post on the editors board the place and date and they should be able to give M/f ratio age range how many are going etc....
Personally I would say give it a go, if it's not for you, you don't have to do it again.
Cindy