[megous]

You can have fearless concurrency in C too if you use async queues and handover data completely without sharing references to data between threads (other than via the queues) - including using thread safe functions.

Rust will not help you with other multi-threadding issues, that arise from how OS implements processes/threads/signals/syscalls etc.

So I wouldn't call it fearless. Concurrent data access is just one issue you have to tak care around.