I'm becoming increasingly skeptical of the "destroying our mental health" framework that we've become obsessed with as a society. "Mental health" is so all-encompassing in its breadth (It's basically our entire subjective experience with the world) but at the same time, it's actually quite limiting in the solutions it implies, as if there's specific ailments or exercises or medications.
We're miserable because our world is bad. The mental health crisis is probably better understood as all of us being sad as we collectively and simultaneously burn the world and fill it with trash, seemingly on purpose, and we're not even having fun. The mental health framework, by converting our anger, loneliness, grief, and sadness into medicalized pathologies, stops us from understanding these feelings as valid and actionable. It leads us to seek clinical or technical fixes, like whether we should limit smart phones or whatever.
Maybe smart phones are bad for our mental health, but I think reducing our entire experience with the world into mental health is the worst thing for our mental health.