> How do we make immutability easy and ergonomic and get rid of nulls in C#? Can we have guarantees in our program. There are even features not in Haskell proper like Liquid Haskell that would be interesting to have in C# or Typescript.

Will any of that be enough to bring the refactoring powers of Haskell? I bet not, you need the entire type system for that, and if you bring the entire type system, your language will become as hard to learn as Haskell.

Without the refactoring powers, you are stuck again into the old school "design it well or you'll suffer" development cycle.