WhatsApp has replaced the PSTN in many countries. Without it, you cannot contact businesses; they simply do not answer normal phone calls. Also, booking accommodation over the internet may require WhatsApp in order to receive self-check-in information, and if you manage to communicate to the accommodation that you don’t have WhatsApp, it may simply cancel your reservation unilaterally.

Honestly I understand OP, I also run GrapheneOS but most of my social life happens on whatsapp and I know it's stupid but I can't change dozens of people's choice to install Signal, even though most of them know the issues with Meta.

My hope is that one day or another whatsapp will enshittify so bad that people will be more prone to move to Signal in the same way that recently Windows got so bad that many users moved to Linux.