I used to want to agree with this, but it simply doesn't hold.
The human brain keeps physically developing until your mid- to late twenties. That means that your capabilities as a person keep developing. Insight, intelligence and even some measure of wisdom aren't effected per say, but things like impulse control, reservation, efficiency and empathy are greatly dependent on the stage of development that your brain is in.
Your example 17-year old may indeed be as mature as you claim, but you should understand that, if this is the case, it is an anomaly, and indication of great hardship in the teen's history, which makes them liable to different unexpected behaviour, at some point.
OP: Sure; you could be a raid-leader. Age isn't everything. But you should first be aware of the limitations of the brain, your limited capacity for judgement at the moment, and be sure not to overextend.