VScode F# plugin and Rider also have much more resources into them.
Then 20 years of production code to chose from.
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.
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.