You are describing a state of software development that has existed since the introduction of punch cards.
Practically every business I’ve worked at has had some internal library or repository of commonly used behavior that can be included in day to day projects.
The problem with this take is the assertion that LLMs are going to take the place of secretaries in your analogy. The reality is that replacing junior devs with LLMs is like replacing secretaries with a network of typewriter monkeys who throw sheets of paper at a drunk MBA who decides what gets faxed.