Jeroen Moons shares his advice for getting a legacy codebase under control. It’s full of great information, and my favorite quote is on how the code base came to this: (Emphasis added)
As you poke and prod the area just past the warning sign with a stick, you might wonder: how on earth can anyone have let this happen? Someone must have seen this coming, surely? Were the people who wrote this code that incompetent?
Possibly. But not more so than anyone else. When push comes to shove, however confident people might seem, nobody else knows what they’re doing either.
The whole article is a great read and should be beneficial for when you are tasked with taming the legacy beast.