I will admit I haven't read all of their posts, but what Haidt & co highlight is basically the conclusion that I've come around to: that yes, smartphones and social media are the problem. Depression, anxiety, attention span...
There was a Dutch comedian the other day who made a good point: when someone beats their child in public people will step in and say something about it. But when in a restaurant little Timmy is put in front of an iPad to shut up for three hours and the teenagers can just TikTok the entire evening, nobody bats an eye.