This week, Mark Zuckerberg took the stand in an antitrust trial that could result in the breakup of Meta’s social networking empire. It might be years before the nearly 3 billion users of the company’s flagship app Facebook—known internally as the Blue app—learn the fate of the service they still use, despite the constant obituaries. (For the record, two years ago, Tom Alison, who heads the service, issued a statement affirming “Facebook is not dead nor dying.”) But with all the hubbub surroundi...