Those seems to be independent issues. Fil-C is about the best way to compile/run C code.

Rust would be about what language to use for new code.

Now that I have been programming in Rust for a couple of years, I don't want to go back to C (except for some hobby projects).

Fil-C is slow.

There is no C or C++ memory safe compiler with acceptable performance for kernels, rendering, games, etc. For that you need Rust.

The future includes Fil-C for legacy code that isn’t performance sensitive and Rust for new code that is.

doesnt it only work on x86_64?

I wish, we will have something like Fil-C as an option for unsafe Rust.