GrapheneOS is made for people who still need some Google products. You can run everything full Google mode, with Playstore, GCam, etc.. But better and privacy-respecting.
Of course not installing anything Google would be even better. But that's it: with GrapheneOS you have a choice.
Been running it for years and I'm still using Gmail and Maps. No issues. There's lots of info surrounding the topic of using Play Services etc on GrapheneOS.