More like saying parents are at fault when a gun salesman enters their home every day, talks for hours with their children, and sells them weapons.
Have these parents tried to not let the salesman in?
Your argument is conflating smart phones with social media apps and you seem to be assuming that kids wouldn't have access to their phone in other locations where they are unsupervised, subject to peer pressure, etc.
The "just say no" argument, basically.
The salesman is at their friends place. And is a prerequisite for soccer team meetups. Etc. You need most parents to cooperate to bar him... but yeah I guess being prudent at home helps.