These are all great points. And my take on seeing these debates about the effects of social media is that too many people tend to fall on one or the other side of a false dichotomy: social media is the root of all evil, or social media is being used as a scapegoat and the effects are grossly over-exaggerated. My opinion is that social media is a contributing factor to much larger problems in our current tech driven society. It shouldn't be blamed for everything, nor casually dismissed in these important discussions.
My other related hobby horse is parenting. I have seen so many people who literally mentality handicapped their children by giving them tablets instead of raising them so that they can watch TV or surf the web themselves.
American parents watch an average of 4 hours of TV per day.
Alternatively, I have friends who don't have tvs or tablets in their house and the developmental differences are night and day.