If you have a rational argument that proves that debuggers are only useful on poorly designed code then I would certainly be interested in hearing it. It is true that the worse the code the more frequently you need to debug, but that's a quite different proposition.
I'm not saying they're only useful there. But we both agree that they're very helpful in understanding a bad codebase. That's because they make bad code easier to handle. Which for some people removes the incentive to clean it up. Basically, they use debuggers as crutches.
