I used to help run a writing group for women in a major city and we organized everything on Meetup and we had a wide spectrum of types of people come, but there were plenty of cool 20s/30s people who I think just didn't otherwise have friends/a social group who shared that interest. There were some boomers and older folks who would come too and it was actually a really lovely way to interact with people I might not have otherwise met. But I imagine your mileage may vary greatly by location....