I disagree. The dream of getting a higher level picture of code is pervasive. E.g. UML was born to do exactly that. However, our modules usually do not compose cleanly, so you cannot visualize them as connected black boxes.

One common followup argument is that functional programming is great for this, because pure functions can be treated as black boxes. Sorry, but the problem is on the algorithmic/business logic level, which cannot be solved by the choice of programming language/paradigm.

Example: Remove data from one database and put it into another one, transactionally. At any point in time any other process must see the data in exactly one of the two databases. You can not merge the databases into one.