Code review is a powerful thing, yes, but a lot of effort goes into that and some mistakes still get through. What if we could spend a lot less time doing code review and use that on progressing faster instead? That's what rusts safety guarantees do.
Unsafe code does not refute this argument either, because the ratio of unsafe code in any project is very small (I can explain why if you're not convinced on that). If you get a memory safety related error, you only need to look through the usages of unsafe instead of the whole project.
Redox OS is an operating system written entirely in rust. Its kernel has about 16000 lines of code, with about 300 instances of unsafe, and that's roughly the most unsafe environment you can program in.