Honestly, I haven't seen anything like that level of issue recently and I strongly suspect the issue here is Civ Six itself.

The last multiplayer game I played was Halo infinite. It went great. Did exactly what it's supposed to.

ETA: I am on Windows... At a cursory glance it looks like changing the download region fixes an issue you encounter in MacOS after updating the operating system. Apple being an also-ran platform for desktop gaming is a long-standing issue completely independent of whether we're in the era of cloud and patching.