Maturity isn't everything, particularly on this forum.
Yes, teenagers are immature, compared to how they will be later. But I've known some very immature people in their 60's, and some very adult 8-year-olds. So it depends on the person. Maturity provides the experience to handle a greater variety of situations, but it doesn't make you smarter.
The younger teens here certainly lack the perspective of the older posters, but generally do just as well with presenting and understanding arguments, and I don't respond differently to posters based on their age.
I never dismiss input from a 13-year-old on this forum, based on age alone. Actually, thinking about it, I don't dismiss anyone's input, ever, based on their age alone, including in person. I've lost arguments to 6-year-olds, admittedly often on the subject of dinosaurs. If someone has something useful and insightful to say, they should be heard and respected.