In the example given it's possible to write a similar library in C to protect against unwanted side effects or bad API design. I'm sure several have been written over the years.
Rust is a great language with lots of improvements over other system programming languages, but that is not going to be enough to get people to switch. You have to show that it's good enough to be worth throwing away 40 odd years of experience and well understood best practice. Something that is going to take a long time and big public projects to do. If just being better was good enough Plan 9 would have been a roaring success and Linux (if it happened) would probably be a footnote in history.
C and UNIX have survived as long as they have not because better alternatives haven't come along, but because the alternatives haven't offered a compelling reason to switch. Unfortunately at least now Rust is falling into the same category.
See also: Niccolo Machiavelli, The Prince