Dabbled with Rust a few years ago. It was not a true joy coming from the C#, Java, Javascript world because it was comparatively verbose to do similar things. It felt like it was meant to be an improvement on the C development paradigm.
And most stuff SS14 devs are trying to enforce in their custom C# engine comes for free in Rust. ECS? Mandatory. Systems can't store state? By design in Bevy - systems are functions. Components need to be ported from class to struct? In Rust you don't have to choose.
That said some issues like faster iteration and sandboxing might make more sense for a C# engine, but so far there wasn't some huge obstacles for developing other kinds of games.
Additionally I see a possible future with automatic memory management + linear types for low level coding, like Haskell and Swift are looking into, as more interesting.
The sweet spot of productiviy of automatic memory management, with the control of type system for low level coding, if really needed.
As an aside, there's https://github.com/StarArawn/kayak_ui that seems nice, but I've not actually used it, so I can't vouch for it.