It being updated frequently just shows it’s being regularly maintained and improved.
C# has many of the same security and safety advantages that Rust does given they are languages with memory management and other safety features built-in.
Rust has exactly the same problems with depreciation as many Frameworks rely on experimental features which are subject to change.
Edit: plus if you have ever used Rust it’s a pain to learn and use compared to C#. C# is so similar to Java and so much easier than C++ that it’s really not much of a jump for programmers new to the language.