> I would assume trivial means the default approach works for most cases. Perhaps mutable global variables are not a common use case. Unsafe might make it easier, but it’s not obvious and probably undesired.

I'm a Rust fan, and I would generally agree with this. It isn't difficult, but trivial isn't quite right either. And no, global vars aren't terribly common in Rust, and when used, are typically done via LazyLock to prevent data races on intialization.

> I don’t know Rust, but I’ve heard pockets of unsafe code in a code base can make it hard to trust in Rust’s guarantees. The compromise feels like the language didn’t actually solve anything.

Not true at all. First, if you aren't writing device drivers/kernels or something very low level there is a high probability your program will have zero unsafe usages in it. Even if you do, you now have an effective comment that tells you where to look if you ever get suspicious behavior. The typical Rust paradigm is to let low level crates (libraries) do the unsafe stuff for you, test it thoroughly (Miri, fuzzing, etc.), and then the community builds on these crates with their safe programs. In contrast, C/C++ programs have every statement in an "unsafe block". In Rust, you know where UB can or cannot happen.