While I believe this is largely correct, it does not support your conclusion.
You are assuming that the participation would need to be to the benefit of the community to be worthwhile. That's not the case. The party which stands to benefit most is the teen themselves. They may not be able to meaningfully participate in the kinds of discussion examples you have listed, but they could try.
After all, not being an ignorant dumbass is a skill that must be learned, and one that (as evidenced by this thread) many adults never managed to learn for themselves.