Couldn't it just be that, uh, Facebook is kinda boring? Or, as the article mentions, that "depressed feelings and lots of time on Facebook [...] go hand in hand," in other words, lonely/isolated people habitually look for connection on social media, but the kinds of communication that happen there are not very interesting or loneliness-assuaging.
David Foster Wallace's 1993 essay "E Unibus Pluram" describes a similar tendency but with television as the substituting technology:
"Every lonely human I know watches way more than the average U.S. six hours a day. The lonely, like the fictional, love one-way watching. For lonely people are usually lonely not because of hideous deformity or odor or obnoxiousness—in fact there exist today social and support groups for persons with precisely these features. Lonely people tend rather to be lonely because they decline to bear the emotional costs associated with being around other humans. They are allergic to people. People affect them too strongly. Let's call the average U.S. lonely person Joe Briefcase. Joe Briefcase just loathes the strain of the self-consciousness which so oddly seems to appear only when other real human beings are around, staring, their human sense-antennae abristle. Joe B. fears how he might appear to watchers. He sits out the stressful U.S. game of appearance poker.
"But lonely people, home, alone, still crave sights and scenes. Hence television. Joe can stare at Them, on the screen; They remain blind to Joe. It's almost like voyeurism."