I think that people aren't giving enough credence to the reason Utah gives for the restrictions: The teen mental health crisis.
Social media has radically changed the social lives of adolescents, and as a result anxiety, depression, self harm, and suicide have all skyrocketed. The data on this is not ambiguous [1].
And there's now a lot of evidence that social media and smartphones are the cause of the crisis: they screw up childhood in a way that has serious health consequences [2].
Time spent in person with friends by 15-24 year olds has dropped from an average of 155 minutes per day in 2003 to an average of 42 min per day in 2019, a drop of 3x [3, figure 4]. How could that not have huge effects on psychological health?
I think these restrictions are a good thing - it's a crude approach and will have some negative consequences, but the scale of the health crisis requires something to be done.
[1] https://jonathanhaidt.substack.com/p/the-teen-mental-illness...
[2] https://jonathanhaidt.substack.com/p/social-media-mental-ill...
[3] https://jonathanhaidt.substack.com/p/the-new-cdc-report