> I went on holiday with someone a few weeks ago who is toughing it out with a no-Whatsapp dumbphone. He missed the train home because he got locked out of the holiday cottage and couldn't get in touch with anyone.

While WhatsApp is definitely the default messenger in many European countries, SMS and calling still exists and works on every phone. It'll cost you extra because of carrier shenanigans, but it's not like nobody has phone numbers anymore because of WhatsApp.

You may be left out of group chats if you don't share the same group chat app, but not being able to get into contact with anyone shouldn't happen.