I really can't see how weed has negatively impacted my growth. I have a 4.0 gpa, I work out every day, I play two instruments, I have good relationships with my family, friends, and co-workers, and I'm in four different clubs at school. I totally understand how you would think that, but if you knew me personally, you'd know I'm doing fine. But I mean that's the thing, you don't know me personally. I can say: "I'm fine" and you can say: "No I bet ur not" but it doesn't really matter because we're just two random dudes on the Internet.
The issue with the matter is that the difference is intangible. You can't know what would have happened if you did something different, because you didn't do something different. Maybe the difference is negligible: maybe it's limited to the time you've spent using drugs rather than doing other things and the differences in experiences. The thing is, while your brain is still growing, it's especially susceptible to developmental rerouting. For a clear example with sound scientific research,
it increases your risk of developing schizophrenia in early adulthood.
That being said, you're still you and can/should make your own decisions. I'm not a fan of the status quo as far as 'kids need to be told what to do' goes. Children, particularly teenagers, are people too. They have wants, desires, needs, etc. and they should have the freedom to pursue them to whatever extent they desire unless it interferes with others.
In short, nobody should be able to tell you what to do just because you're younger than them.
I do think it would be
irresponsible to not follow advice, but on the scale of irresponsibility, smoking weed while developing weighs a lot less than plenty of other things people in this very group do on a regular basis.