I think the best take-home from the article is simply that your screen time is a problem only if it's distracting you from the things you'd rather be doing.

If you're spending the majority of your Internet time researching a specific topic, or interacting with others online about that topic, or something you're specifically interested in, then there's not really a problem. As you say, the alternative is spending time offline focused on something else, and neither online nor offline is inherently bad.

It's only bad if you're online and you want to be e.g. watching a Coursera video or having a language lesson over Skype, etc., and the incoming Facebook chat messages, tweets and Slack notifications are constantly pulling away from your intended purpose.