This is spot on—a simple and precise explanation. As a programmer myself, I’ve seen developers dive into a 15-year-old codebase, independently work through it, and only ask questions once they’ve exhausted all other options.
Is this what people think of when they think of an old codebase? Must be nice :')
15 years of active feature development on the other hand will likely be a major slog for any developer, regardless of experience. There's a lot that can happen in 15 years even if there were only 1-3 developers if they everyone takes the easy path since they know where all the gotchas are. It's only when new devs are added that the curtain comes down and the lazy abstractions (or lack thereof) are exposed.