To be devil's advocate, I have 3 children.  With my oldest daughter we strictly monitored screen time.  My son basically has free range of screens.  My youngest daughter is only 18 months old so screens aren't really a thing.  In my experience with both older kids, excess screen time absolutely correlates with poorer behavior/mood.  However, my son is less affected by this... presumably due to having so much access.  My oldest is in high school so she's had a phone now for a couple years.  I also police how much time she gets with it because when she has it, the world around her ceases to exist.  My son isn't that way at all and will focus when you talk to him.  My problem now is that my daughter is 17 and I KNOW she needs more access and time with her phone... but any time I give it to her longer, she doesn't get the other stuff done that she needs to.  So, I agree I like less screen time, but I also still know nothing lol