Going by your first sentence, you must be working in a very bad environment. How can anyone solve a problem they don't understand?

Hint: They don't

They usually code for the happy path, and add edge cases as bugs are discovered in production. But after a while both happy path and edge cases blend into a ball of mud that you need the correct incantation to get running. And it's a logic maze that contradict every piece of documentation you can find (ticket, emails). Then it quickly become something that people don't dare to touch.