Screen time might encompass video chatting with a relative, reading a book on the Kindle app, watching a 2 hour long documentary, watching a 10 minute long tutorial on YouTube, writing an email, editing pictures of one’s vacation, managing one’s finances through a webpage or spreadsheet, etc etc etc.
Sure, there are always things you can do on a screen that are productive. But you need to way the difficulty of managing these activities with the potential upsides that only a screen can provide.