How many of those things work well on Linux/MacOS? Rust, Cargo, rust-analyzer, VSCode work on every major plateform. You also have access to the .NET ecosystem but it's not as easy as the Rust ecosystem since most of the packages are C#, not F#, and idiomatic C# and idiomatic F# are quite different. In terms of resources too, F# is quite poor compared to Rust.

Edit: another thing, compiling to native is not really a first class citizen on .NET. That makes it a bit worse to distribute tools compared to Rust, Go or OCaml. Scala also suffer from this.

F# can just use C#, that is the magic of CLR.

VScode F# plugin and Rider also have much more resources into them.

Then 20 years of production code to chose from.

You can use C# from F#, of course, but then you can run into issues with nulls and things like that. There's a reason every programming language has their own implementation of JSON/XML parsing, HTTP and things like that: offering an idiomatic API is important.

Last time I use the VSCode F# plugin (around a year ago), the experience was strictly worse than rust-analyzer. The compiler errors are also not as good. I've never used Rider so I can't comment on that.

You're right about the 20 years of production code for C#. NuGet lists 241418 packages compared to crates.io 61579 crates, and there's a good chance most of them are more mature than the Rust alternatives. However that's C#, not F#, and I doubt F# represents more than 10% of the packages. That's still better than doing it yourself if there's no package or writing bindings to C though.

I still think F# and Scala are solid choices if you want a functional language today, but it's not the "garbage collected Rust" ideal I wish we had.