C# and F# are not C replacements but Zig Is
Different languages serve different purposes. That is why we have languages like C and Zig.
I am well aware of what is going on in Microsoft land but as I've said I think Swift is a better language than C# if you want an statically typed object-oriented language. Personally I prefer Julia in most cases. You should check out Julia, it is quite unique as it is a dynamically typed language which frequently beats C/C++ and Fortran in performance.
As for why I am writing about Zig, you got to look at the title. It is a replacement for C, not a replacement for any language out there. If I am doing data science or machine learning e.g. I am not going to be using Zig, I would rather use Julia.
However a lot of work in this word requires a C-like language. If you are writing an operating system kernel, then C# isn't going to cut it. If you work in small embedded systems with limited memory, C#, Rust, Go etc are not going to cut it either. With Zig you can make 15kb binaries with no dependencies.
For me Zig is interesting as a hobby language. Not professionally. I like ocassionally working on microcontrollers like AVR/Arudino. Typically you program some real time system, where need complete control over time. You don't want a garbage collector suddenly kicking in causing your perfectly timed stepper motor to stall.
I have also worked with people doing things like video codec development. There you also need perfect timing. Every frame counts. Again you cannot have a garbage collected system.