From a language architecture standpoint and not an ecosystem standpoint, what might be some things where you’d really not want to use Rust, either because of some limitation that prevents it from doing it or just because it’d be massively annoying to write to the point of significantly reduced productivity? What about Rust makes it unsuitable, and what language paradigms are the best for it?

I hear a lot about how the things that Rust is not good for, JIT compilation with a garbage collector is usually the best solution, and vice versa. How true is this?