In other words if I leave my kid alone in the house with a liquor cabinet, and the kid gets drunk every day, did the liquor do the harm or did I?
That's an imperfect analogy though, because -- at least in the U.S. -- our society has already aligned itself such that our institutions and our devices raise our kids, not our families. As long as we keep that norm, then in a nation that values free speech and capitalism as much as the U.S. does, we're certain to have this problem.
So as another commenter said, if we ban TikTok something slightly more benign will take its place, and that's because we aren't dealing with the real issue: we don't raise our kids anymore.
Personally I look at the commonality of nuclear families[1] as a big culprit here. Once you isolate kids from aunts, uncles, cousins and grandparents you're left with just the parents to raise them. Those not rich enough to afford daycare have to either split the duty so they can afford a roof over their heads or leave the kids alone.
[1] https://en.wikipedia.org/wiki/Nuclear_family#Compared_with_e...