I think one notable difference for Rust is that it's still perfectly possible to call async code from sync code. It might be slightly less efficient than if eve

I think one notable difference for Rust is that it's still perfectly possible to call async code from sync code. It might be slightly less efficient than if everything was participating in async, but often that's fine when it's just the one-off network request in your otherwise synchronous CPU-heavy workload. Meanwhile, for people who need to have no GC, you can't paper over an internal dependency that uses GC. The whole stack has to be no-GC period. A similar comparison in the Rust world is probably with the #![no_std] ecosystem. Kernels/kernel modules and super low power microcontrollers have the biggest restrictions on what libraries they can pull in, since they can't use any dependencies that use the normal standard library, only the core library. (Low power is relative though, eg the ESP32 chips have nearly full std lib support)