For me, it's just a question of ergonomics.

Can Rust do what C# does? Yes, unquestionably. But there is a value to a runtime and GC. It makes writing application code a bit easier, more assumptions can be made, and less care needs to be given to memory.

It's suboptimal, but usually doesn't matter. I'd rather write a backend in C#, and the performance is usually more than good enough.