Here's the trouble with this article. I fear this problem will only get worse. In the first paragraph, various authors are quoted from the 20th century. Except for Putnam and a few of those after, I've never heard of any of them. Yes, it is clear that the idea of a loneliness epidemic is not new, but simply because it was mentioned and/or identified in the past, without more context around the citations (there have always been "fringe" authors, even the Greeks had them), it is not convincing that it was a mainstream problem before e.g. Putnam and others.