C# is missing expressive types for me.

That might land with native unions but it's not there yet. There's workarounds with OneOf and Dune but those are kind of messy.

I think expressive types on dotnet are possible - I am a big fan of F# and those types are very good. So I think C# will get there but I can't say it's there yet.

Once union types land, it will just need first class support for checked errors instead of unchecked exceptions flying around everywhere.