The point is that memory issues are a smallish number of issue compared to the larger ecosystem of vulnerabilities, and choosing to port everything to Rust is like over-optimizing. Well, that’s my 2 cents.
For a language as ugly as Rust, my thought is that people should actually be using Ada, and have a mathematically provable correctness angle; not just a replacement for C/C++ with memory safety.
Rust and Ada are about equally safe, both have advantages and disadvantages. Perhaps you're thinking about SPARK ADA, but that's a different kettle of fish.
It's a bit like saying you should program in C, because formal verification tool X generates C code hence C is safe.
Rust is a beautiful language. Gorgeous.
> The point is that memory issues are a smallish number of issue compared to the larger ecosystem of vulnerabilities
If memory safety issues are 75% of exploited zero days it sounds to me like they're the biggest issue in the ecosystem by far.