GrapheneOS have discussed and explored replacing Google Play/Google Mobile Services functionality with equivalent or open source replacements. See: eSIM management, location services, push notifications et cetera. What they have refused is bundling a privileged component (for full Google Services functionality/compatibility) and enabling signature spoofing support.

GrapheneOS also heavily promote the use of open source Android apps. What they refuse is having app stores that reuse app package names, centralise the signing of app packages, perform reproducible builds on outdated infrastructure, significantly delay app updates et cetera.

I cannot deny your opinion, but just want to suggest that from my understanding GrapheneOS are not against microG and F-Droid as concepts, just against their current implementations.