> use C++ or Rust instead of Java or C# in that case?
Despite having to spend extra time translating C API headers into C#, the productivity gains of the higher-level memory safe language were enormous.
Another example, I have shipped commercial embedded software running on ARM Linux, and based on .NET Core runtime. The major parts of the implementation were written in idiomatic memory-safe C#.
> doing business (especially web) apps
Well, these business web apps are precisely the long-running servers I have mentioned. Still, the software ecosystem is not limited to that class of problems, and due to different tradeoffs Java is not great for anything else.
My point is if you are doing business (especially web) apps. Use one of JVM langs insted of C# because ecosystem is much bigger (and it has fresher langs as well like Kotlin - if that's what you care about)