This is patently false. I run GrapheneOS with no Google play services installed. The only issue I have is no paid app updates and some apps won't send notifications since they ran through Google. I use my phone though mostly as a phone. I have almost no social media and I do not use banking apps on my phone. I choose to use website versions of anything on my phone so long as I can.

Not to mention, the replacement OSes like /e/os and the others don't have the hardening of GrapheneOS. Cellibrite recently was leaked they still can't crack open GrapheneOS.