Yeah, I agree. It's a really common excuse and I think it somewhat diminishes the credibility of those who use it. I don't think anyone's opinion on what constitutes a "truly horrible codebase" should count until they've been a developer for at least 10 years, worked at several different employers, and contributed to several different large open-source projects (which usually have the luxury of rejecting code until they feel it's "right" despite the potential commercial consequences, not something that most other projects get to do). "This codebase is terrible" is a common whine from newer devs and/or people that are just too lazy to put in the time to learn someone else's code.

In the real world, production projects get messy because getting stuff done is more important than building a codebase that represents the paragon of academic excellence. That doesn't automatically make the project horrible.