> Now, who defines "addictive" using which aspect?

Addictive is whatever that creates a dependence that doesn't allow you to function correctly and productively, because it produces a natural reward.

In this case, design patterns that promote and provoke addictions, like gamification, attention grabbing, etc. that kids don't have tools to be aware of, need to be regulated. In fact, sugar content regulation in foodstuff have shown to be very effective at reducing obesity on kids. It's not a "ban", it's a regulation.