This is an interesting point. One of the major things we're trying to demonstrate with Hack Club is we box people in too much based on their age. Especially young people who generally have a well defined set of activities laid out for them before they can start practicing some autonomy (largely from the way schooling works). The hope is that open-source projects like this can show people that there are some accessible routes and supportive communities to help them pursue their passions. Personally I hope the work serves more than just teenagers, but working out the details of serving young people well means as an organization we have to focus on it.

More directly responding to your point Ivan Illich has some interesting commentary on the modern invention of childhood in Deschooling Society.

Historically it’s a new concept. At least for the west but I suspect for human as a whole.

We used to jump from childhood to adulthood without lingering.

I don’t cast any judgment on the concept of teenagehood. I think it’s out there now.