The intention behind configuration languages is sound but there’s just too many of them. Not having a universally accepted one makes picking one harder. Also, migrating from one to another isn’t as straightforward. Plus,

    for database in ["alpha", "bravo"]:
        for period, days in period_retention_days:

At this point, you’re better off writing a Python script that spits out some JSON. I‘m aware that even the blog mentions it. The benefit is - having a more expressive language at your fingertips and not having to fight your peers while trying to add yet another idiosyncratic dependency.