In the two clubs I ride with, one is primarily 40-60+ age riders. The other has a wider variety with riders from their early 20s to 70+. The cyclocross and gravel grinding groups tend to be younger riders and I'm one of the geezers at 50 years old (gravel grinding, haven't tried CX). The A rides tend to have more people in their 20s and 30s and fewer in the 50+ range.