Your making it out as if Heroic is somehow impossible without being carried. It's not. Nor is it a nessecity for seeing the content in the game. There are two lower difficulties if someone finds the task insourmountable or if someone doesn't yet know the mechanics even thou there are hundreds of guides out there. Climbing a ladder is done one step at the time. And the perosn wont learn to climb ladders if i pick him up and throw him up to the highest step.
The 12 year old are not some old granny who cannot survive on her own without aid, he is a 12 year old kid with every possibility to jump into a group of people who all are on the same experience and progress throu the raid just like everyone else has.
My parents didnt carry me throu heroics, i climbed that tree all on my own. As, i suspect, did all these mythic raid grps that sprint hc for echoes.