It's really a demographic issue. I've found that in the US relatively few people use WA. Same for SEA. But in western Europe almost everything is done on WA.
From "neighborhoodwatch" via "the school information" to "colleagues". Hell, even governments and public transportation have "feel unsafe? message us on whatsapp 06..." In the Netherlands it's truly omnipresent, and without WA you will be left out socially.
I'm reluctant of WA, because I'm steering clear of Meta as much as possible, but I do use it to: keep in touch with at least 26 social groups - friends, family, colleagues, co-workers, business - keep in touch with my date/love, my mother, and father who lives across the world.
granted, there's a big move going towards signal lately - finally. But I'm not sure how big this really is, and how sticky it will prove. Nor if this is just my bubble or truly across the whole country.
Even within the Netherlands there are pockets of Signal users, Telegram users, and in rare occasions even people using SMS or iMessage. Facebook Messenger also has a foothold in some circles.
That said, you'd be an outlier if you have a mobile phone but no WhatsApp. Everyone has WhatsApp, but fortunately not everyone is using it for everything. Unfortunately, that usually means using an even less secure and trustworthy messenger service.