Comment by bhk

Not just the string-related functions. If you want robust error checking, re-entrant code, and bounds checking performed in library functions (instead of performing bespoke validations all across your code base), you have some work to do. Yes, some improvements have been tacked on over the years, but many problems ("current locale", for one) remain endemic.

In my experience, the worst part of the C standard library is not its existence, but the fact that so many developers insist on slavishly using it directly, instead of safer wrappers.