> Now, admittedly, not all the productivity gain is from types. However, they certainly help me, not just in making the code robust but also in writing it in the first place. And typeclasses actually do make the language concretely more expressive in certain ways.

You said you started out in Racket. Did you try Typed Racket? You don't necessarily need to move to Haskell to get a type system (though you won't get typeclasses).