Like a subroutine
The trouble lies in that management in general deals with projects in terms of the budget and the schedule, money and time; Everything has to plug into these Management Interface Sockets.
Management, not Engineering The problems you are trying to address are problems of Software Development Management, not a literary problem of what simile to choose. Can you imagine if the people who built the Pyramids had started by trying to think what kind of a stone was like a subroutine, and what kind of chisel was like what kind of interior design software abstract toolkit. That’s how the construction people did it. Get yourself past analogies into software development. So don’t bother dreaming up the perfect analogy. Eventually, everybody will be taught programming as soon as they’ve learned algebra, and we won’t be forced to compare subroutines to drainpipe, and object broker frameworks to infinite pyramids of prefab housing within housing.