In what concerns me, although I like Rust, I only see it for scenarios where any kind of memory allocation is very precious, Ada/SPARK and MISRA-C style.
I have been using GC languages with C++ like features, or polyglot codebases, for almost 20 years to think otherwise.
Most of the time developers learn about new and miss out on the low level language features.
It is a matter of balance, either trying to do everything in a single language, or eventually write a couple of functions in a lower level language that are then used as building blocks for the rest of the application.
No need to throw away the ecosystem and developer tooling just to rewrite a data structure.
For example, you can do codecs in C# on WinRT with .NET Native,
https://docs.microsoft.com/en-us/windows/uwp/audio-video-cam...
In the context of protobuf,
https://devblogs.microsoft.com/aspnet/grpc-performance-impro...
Back to Rust, yes it is a good option, I just wouldn't write the whole application on it, just specialized libraries.
Hence why I am looking forward to Rust/Windows efforts.
From the same author, a zero-unsafe arena allocator: https://github.com/fitzgen/generational-arena
There are many, many arena implementations available with varying characteristics. It's disingenuous to act like Rust requires the author of an arena library to write "unsafe" everywhere.