In my experience there is not much to know about the ACD parts of ACID, because they're just guaranties that are obvious to want and which will naturally make your life easier.
The I (Isolation) part is the one you'll need to understand whenever you scale up to a point where concurrency starts to become non trivial in your product, mainly because there are multiple levels of isolation, which each provides different guaranties, and you'll need to understand what level your database uses and what it means for your application.
As for the overall point of the article, it's just a question of scale. The more you scale the more you need to cut through the abstraction to understand what the hell is going on. Hire accordingly.
They may be obvious to you, but you'd be surprised at how many people out there are doing stuff without optimistic concurrency control, locking or transactions. I mean Mongo only added transactions for updating multiple documents relatively recently. Plus from what I remember they originally missed out the "D" due to only writing to disk intermittently.
The I (Isolation) part is the one you'll need to understand whenever you scale up to a point where concurrency starts to become non trivial in your product, mainly because there are multiple levels of isolation, which each provides different guaranties, and you'll need to understand what level your database uses and what it means for your application.
As for the overall point of the article, it's just a question of scale. The more you scale the more you need to cut through the abstraction to understand what the hell is going on. Hire accordingly.