"The biggest complexity is that Git has a very conservative approach to compatibility, requiring that repositories remain compatible across versions."
This, above all else. That I never, or anyone else on our team, ever has to worry about wether they are running an "older version" of git is such a win.
It's not really a surprise that monorepo advocates struggle here. Compatibility through versioning and stable APIs is challenging and requires discipline.
Making wide-spread changes to all clients of your code when you make changes that break things doesn't require discipline.
This, above all else. That I never, or anyone else on our team, ever has to worry about wether they are running an "older version" of git is such a win.