Writing vectorizable code is certainly important for some use cases, but it’s not relevant for the majority of programming tasks, even in systems/infra programming. Most things outside of numerical work just aren’t bound by the effective width of the core backend.

Rust doesn’t have to solve every problem in order to be useful. The major problem it does solve (relative to C++) is explicit compile-time tracking and enforcement of the scope of object validity, preventing (or at least making more unlikely) a class of bugs including use-after-free, uninitialized reads, buffer overflows, dangling pointers, and so on — without requiring a garbage collector.

This C++ code, a real mistake I’ve seen in the wild, would be totally impossible to write in Rust without explicitly using the “unsafe” keyword:

    SomeType* foo()
    {
        SomeType x;
        return &x;
    }

None of this has to do with vectorization, but it’s still important and useful for many tasks.

(As an aside: I would be curious to know if there are any languages that make it easier to write auto-vectorizing compilers. Personally I’ve never seen numeric tight loop kernels written without explicit use of architecture-specific intrinsics and/or raw assembly language. But I’ve only worked on that sort of code for at most a few months in my career, so I’d be happy to learn if there’s research in this area.)