WhatsApp? I haven't heard of anyone using it where I lived, but I wouldn't be surprised if some people were using it more. But like The Greatest Kiwifarmer said, many Gen Z prefer using social media like Instagram, and there's a few stragglers on snapchat, but I haven't used Snapchat since early high school. Whenever I bring up WhatsApp people look at me confused, since I use it for international friends

I am curious if more people use it. There is a little reputation that some of those messaging apps, I believe Kik earned that reputation in my location, that some are used for drug deals. For our churches, most use Facebook Messager. Most of this from me is also anecdotal for my part of the United States.
I truly would say it depends on your country and location within your country. I'm a zoomer and I believe that many prefer using Instagram for messaging in my area. I guess some will move to WhatsApp but I wonder if it will happen.