Agreed, but the point is that FB's algorithm optimizing for "engagement" is in fact also optimizing for addiction[0]. And so are many others of a certain type of industry that includes YouTube, FB, Instagram, etc. It's not quite social networks, but a common factor seems to be that they're ad-funded and highly automated.
[0] and I believe it is currently way beyond our state of the art to design an algorithm that does not have this unwanted property.
That's debatable. I think people who spend hours pouring through pictures from thousands of acquaintances and commenting can be considered addicted, especially when it becomes difficult to get their attention from it. I see it with people over 50 most often, I think because of an internal desire to feel connected with people who they drifted apart from years ago, or to live vicariously through others.
Also "engagement" is not the same as addiction. People who follow more close friends are more engaged on FB, but they are not addicted.