Perhaps not for most applications, but I think it actually is for an OS. Operating systems are pretty tightly tied to the paradigm of their systems programming language, and possible memory-safety guarantees is a strong feature for an OS as well.
Either way, general grumpiness about Rust being used to write an OS may be a reaction to the hype, but plenty of people have expressed interest in an OS written in Rust, if not for any other purpose than to challenge Rust's basic claims.
Besides, there are many many factors determining successes of OSes, often far removed from quality of the software itself (1986 AmigaOS had GUI and multitasking, and still lost to MS-DOS and Windows 3.1).