Sounds like you getting ready for a century. That season is quickly approaching.

I don't think it matters where you are with respect to this group, some folks here may do a true average of 15 mph but when you find they are doing this over a 50 mile course with 4000' of climbing, that's pretty good, others are flat landers that looked down at their speedo once and saw 20 mph and report that as their average speed, so you just don't know.

Your question was how well are you doing with respect to other older riders, the answer is simple - your data suggests you are way better. But that is not the question you should ask, the real question is, what are your goals and how do you achieve them. Are you more interested in smiles over miles, are you more interested in riding with a group, or are you a hard core racer. the answer to these questions will guide you to a happier place on the bike.