Not solving all security issues isn't the same as not solving security issues. I'd rather my financial data be handled by software written in something that solves many whole classes of vulnerabilities than something that solves none of them.
I want to point out one more thing: Rust is not a simple language by any stretch. It's equal to in complexity to C++ (yet without decades of established "good practices"). It is much preferable to have an easier to understand core and move the complexity outward—for improved stability and robustness. The core OS by nature of what it does needs to access raw resources in an "unsafe" manner. Rust kernel code will be littered with unsafe blocks and unnecessary complexity.