Utilizing Google Play Services in GrapheneOS is certainly better in regards to data harvesting that happens on stock devices. But imagine how much more private you are by not using them. You should stick to running privacy friendly services and apps that have a good track record and are recommended in privacy community, not saying you have to. Only by exercising restriction in your use of these apps and services you can achieve a positive result. When I look at the supermarket shelf, I see thousands of foods I can potentially eat, but know, that not all of them are going to help my overall health so I am cautious and choose to stay away from many. I do not wish to biohack my health by eating certain superfoods, yet predominantly remain on a junk diet supplied by Big Food and Big Pharma. Do you get my point?