I agree that unfamiliarity should not awful a code base make.

However, there are degrees, and probably thresholds. If your code to manage web site users is using string theory, despite the assumedly concise, elegant and refined code, it would make it awful to all programmers, but the two in the world who master both programming, web site user management and string theory.

Otherwise, bad design patterns and bad coding practices definitely characterize awful code bases.

But the worst, is when it’s so bad that you can hardly refactorize it.