I don’t think there’s a huge benefit in using GrapheneOS over Apple for “privacy reasons” its more about the apps you actually install, and I don’t think GrapheneOS has ever marketed itself in that way.
It’s mostly anti-Apple rhetoric spread by people who want to find reasons to not buy Apple. Personally I don’t use apple products and I have none because I don’t like vendor lock-in to that ecosystem however for aged people specifically that are used to those products I don’t see it as a massive “privacy downgrade” to continue to use those products.
What I would keep in mind is any product you recommend, you will be on the hook to support.