A much better tactic, and one that I see neglected far too often is to instill the reasoning into the kids from a young age, don't bar them from what's bad from them, teach them that why and how it's bad so they themselves keep a distance. My parents did his very effectively with me and my siblings, and we, despite our age and frequent exposure to such things, naturally gravitate away from obsession. And this isn't just a niche case, there are many people, even in my generation, who are waking up to the reality and behaving in a similar manner, although it's hard to get that fact out there with all the stigma surrounding basically any teenager nowadays.
And saying that this strategy "doesn't work" or is "too hard" is usually just cope for parents with poor skills in my experience.
>Watch them cry and talk about how they'll be social outcasts and their friends will mock them, or moan about how they need it for school to check the Facebook page their teacher posts assignments to.
I genuinely can't tell if this is some sort of meta-ironic take but no, just no. The vast majority of even elementary school childrens' lives are being moved online slowly but surely, and whether you like it or not they are going to have to pull out that laptop or phone for hours a day, can you sit and watch them for that entire time?