I don't think F# is that second class anymore especially if you are developing on Linux/Mac OSX. The more concise language/syntax is a big plus when you don't want the heavy IDE and want to be cross platform. The VS Code plugin for example seems more mature than Omnisharp and while like any other Code plugin less flaky than many of the others.
I think there's at least one way in which F# is a second-class citizen: documentation. The documentation for anything in .Net will contain code in C#, but code in F# is quite rare.
So if you want to use F#, I think you still need to be able to read C# code.
It might not be full second class but I dunno I'd go all the way to first class. For example F# doesn't support the source generators feature that came with .NET 5 (unless they added it in 6 and I missed it but when I looked at that post you linked I didn't recall seeing it).
They got type generators which somewhat influenced and predates the Source Generator feature by a few years. Not the same thing of course, and from what I've seen are slightly different in target/scope. (e.g. F#'s seems more appropriate for scripting where you can use it without a proj entry).
Do you mean type providers? That's their own type of nice thing but to your point it is only for generating types, source generators can generate much more than a basic type. Also I swear I saw somewhere type providers were not functioning as well in newer .NET but that was hearsay as I never tried them in 5 and now 6.
