WhatsApp is the most common worldwide, but not the most common in every country. That could be Facebook Messenger, Telegram, or even something like LINE. (Yes, Messenger and WhatsApp are nearly the same thing these days.) If you have friends from different places you end up with most of the messaging apps installed on your phone.
Came here to post the same. 90% of my messaging is WhatsApp, 10% Telegram. The only thing I use SMS for is 2FA and even that is dying out in favour of push notifications.
Haven't used SMS in 10 years. I had to send a SMS to opt out of one of my carrier's options and I had to do the whole setup for Adnroid's Messages app because I have never opened it.
