Would be nice if these kinds of articles would at least take a paragraph to plug some alternatives, such as Signal.
As always network effect will be the problem. I know plenty of people on WhatsApp and almost nobody on Signal
Network effects aren't a big deal when it comes to messaging. There was a time when people thought iPhone wouldn't be able to overcome Blackberry because everyone was on BBM. In the last couple decades we've seen people go from ICQ to AIM/Yahoo/MSN to Google Talk to Skype to Facebook Messenger to BBM to Whatsapp/iMessage/Instagram, with dozens of smaller options like Kik, Viber, Line, Signal, Telegram all hanging around. It doesn't take much to cause another shift in the space.