The concurrency design in Haskell is cool, though I gotta admit that I don't find it much fun to write.

It's not because the language is "hard". I remember when I first learned Haskell a million years ago I thought it was the coolest thing ever because I had never seen anyone work at that abstract of a level before, especially in a compiled language. I got to understand the theory well enough and I know how to write a program with it, but the entire language kind of feels slapped together to me. Every time I've written anything in Haskell, I feel like I have to do a million compiler extensions, or rely on third party libraries' liberal use of Template Haskell (e.g. Lens) to make the language feel anywhere near "modern".

Yes yes yes, I know this is a complaint about GHC, not "Haskell", but given that GHC is basically the only Haskell compiler that gets serious use I don't think it's weird to conflate the compiler and the language.