Substance Use Disorder (the new category for chemical addictions) has specifics such as withdrawal and physical dependency that you don't get from turning off your Facebook account.
Facebook is a habit that many people user too much. It isn't like a drug that has drastic and rapid physical changes in your brain. Your brain isn't literally hijacked anymore than TV or anything you like doing hijacks your brain. It reacts fairly normally actually.
Optimizing for somebody to use a site a lot isn't addicting people. The abuse of terminology has gone too far and is really clouding the discussion.
Besides what would it look like to not "optimize for addiction"? Give people news stories they don't want to read? The conversation has just gone off the rails when it starts to be compared to cocaine and heroin.