As a huge fan of Civ IV, I've found the macOS version pretty janky. I have a generally better experience on my Mac by just using Steam In-Home Streaming from my Windows box.

Why is that?

It uses the system python? I doubt it.

It absolutely does and macOS has already broken it several times. This I guess to some extent demonstrates the folly of having one. https://forums.civfanatics.com/threads/how-to-get-civ4-bts-w...