Honestly I don't even know why I'm asking. There's about as much chance of these being answered as there was with SCO CEO guy. What was his name again? I don't even remember. I expect unpronounceable last name guy will be equally as memorable.
It always boils down to understanding the system and having the will to fix it, though. I've worked for companies that were crippled by their bad software. In those companies, no one could explain how the entire system worked, end-to-end. The problems were always "Somebody else's problem" because each team would point their finger at some other component that they didn't know anything about, and that component owner would come back and say "That's not OUR problem!" Meanwhile the companies would not be able to effectively grow or take on new customers because the entire product generation process was so cumbersome and slow.
A lot of these projects had no way to test changes other than to push them up to production and see what happened. The worst offenders had systems that were so tightly coupled that you could only run data start-to-finish through the entire system, which made setting up test systems difficult. In some cases, no one in the company had a complete understanding of the full system.
Even in such situations, it's still possible to drive quality in the system. It requires a whole lot of reading and understanding -- you need to know and understand the business driving the software, the requirements of the business and customers and you have to understand a lot of very convoluted code. You also have to be able to verify changes worked as expected and introduced no other bugs without having to push the software all the way to production to do so. But most of all you have to have the will to actually improve things rather than accept that this is just how this project is. Quite frequently the team in place doesn't have a lot of incentive to have that will -- if the software is ever actually good, it would threaten those fat paychecks they collect for maintaining the mess.
When I left you, I was but the pupil. Now, I am the master. - Darth Vader