I bet C# and F# are actually nice languages and I shortly considered adopting them together with Unity but at the end of the day I was still suspicious of Microsoft, and support for other platforms then windows. The article honestly sounds a bit like a straw man argument. Maybe bloomberg could have made another tech choice but then again I don't know the details.
I also use Rider exclusively and going to Visual Studio on Windows now and then I'm not missing much (visual studio did have some nice plugin for debugging compiler plugins, had to hack around than in Rider)
I can't comment on Unity part.
F# for me overpromises and underdelivers - it all sounds amazing in theory but it's been 3 times over the last decade where I've tried to use it (last time just a few months ago) and it never just works - I've spent diagnosing "why isn't this F# feature working as advertised" than solving my problem (from tooling like F# projects breaking autocomplete in VS solution - even for C# projects, to language features like type providers just being a nightmare to work with and integrate into CI/CD)