The only Google-related services I'd like to use on my phone is account log-in for Pokemon GO and Ingress. My options are a 120MB+ package of proprietary Google apps with max permissions to do whatever and run in the background, or a 4MB microG package with very limited permissions.

I can't use Signal or my local railway app without Google Cloud Messaging. So I have two choices: - Don't use them - Install Google crapware package - Install microG, which supplies the APIs so other apps can function normally

Signal can now work without GCM, they merged an alternative that uses websockets.

microG also reimplements the Google Maps APIs (using OpenStreetMaps) and the Location APIs (with different backends, like Mozilla Location Services or a local offline database). The main Google-based service is Google Cloud Messaging, which is disabled by default in microG.

As you can see, microG doesn't strictly depends on the Google cloud services.

Thanks, this explains things a bit. I think I just misunderstood the scope of this since I'm not in the Android ecosystem.