You've mentioned some problems but there are so many potential issues.
Brain developmental issues
Addiction issues
Social skills development
Problems Self regulating
Constant judgement and comparison
Bullying
Grooming
Content they are fed -neg subject matter
Content they are fed - they shouldn't see
Content they are fed - flimflam advertising/influencer
The amount of time they are simply wasting (look at any of their phone use monitoring apps,

)...it's literally taken over so many sports/hobbies/interests they were doing or could be doing.
All the traits of addiction.
The problem is I absolutely hate the fudging thing (not the phone really, social media and the screen addiction), so I have to keep my anger (yes, it feels like anger) in check when tensions around it arise. I think, as the adult, I can see the multiple problems around it (short and long term) and it's born out of parental protection for my daughter.
The bottom line is, the companies are clams and don't give a fudge.
My worry is, I can easily see they'll be a certain generation that we will look back on as guinea pigs. But the damage will already be done.