There's a great talk that explains how code structure ends up looking like the org chart, and every subsequent organization chart layered on top producing spaghetti code. Windows is now old and full of spaghetti code. Then Microsoft layed off all the expensive seniors who knew the stack and replaced them with cheaper diverse and outsourced staff. Then the people who can't maintain the code use AI and just ship it without any testing.

edit: https://en.wikipedia.org/wiki/Conway%27s_law