I’ve never had a Facebook account, I’ve never had an insta account, but I do use WhatsApp.
Pretty much everyone I know whether old or young uses WhatsApp. When I was travelling, a lot of apartments, hotels and booking services used it too.
Seems to be the one messaging app that cuts across all generations, countries and also the Android/IOS divide.
For general browsing, news, technology, mainstream topics etc… it’s much better than reddit, less toxic, better vibe.
It’s very small though, so I’ve found two areas where it is just not a replacement:
Specific, smaller niche interests, they might have a community here but it is often empty and quiet or just non existent.
Sports, specifically a place to chat during live events. There’s not enough people to support that.
So it depends what you are looking for and how niche your interests are.
I’ve mostly stopped using reddit and am in here now. But I still end up there occasionally. Not much these days though.