Yes, debugging is pretty much the largest part of any software development (same goes for hardware development as well). That's not to say design isn't just as important: a proper design leads to fewer errors that need debugging.

But you almost always wind up spending more time on fixing bugs that implementing features, although it may not seem that way at first, because a poor testing system allows the bugs to hide for longer, so that all the time spend debugging gets spread over the lifetime of the software and therefore the amount of work spent on it gets miscounted somewhat.