No, Grapheneos is quite more secure than stock os when comes to handling google play service if you need to use it.
https://grapheneos.social/@GrapheneOS/113459782313987260
> At the end of the day, once Google stops shipping sec updates for your phone, firmware updates stop so that's it really.
That is true. Graphene does not hide that. If you want to live without any influence of google use iOS/MacOS or Windows.