You can't formulate for everyone - that's Science!
As a brand owner, I formulate products for my specific consumer according to my ethos.
This means understanding the complexities of adolescent skin and hair conditions, analysing the most up to date, peer reviewed, scientific research into ingredients and taking a balanced view on each ingredient to be included.
I receive a lot of positive feedback about the products but one post caught my eye. This is a "really shitty product". The person in question posted a picture on instagram and tagged me in. The complaint was that they still had "dry ends".
As the American's say, here's the thing; Hair is dead, it's dead from the moment it appears from the scalp and therefore the ends are the oldest part. Sometimes Silicones are used to condition dry hair (by temporally adhering to the hair follicle) and these are washed away the next time the hair is cleaned leaving you back where you started. Teenagers tend to have oily hair and if silicones are used it can end up leaving the hair looking lank by the end of the day. I believe that silicones are not appropriate for everyday conditioning of teenage hair.
If you want to address dry ends, my advice would be to look for a product that claims to condition dry ends.
No cosmetic product will suit absolutely everyone, that's the nature of cosmetic science.