Haskell is a lot of fun, but as yet not useful in any practical way. People will argue with me of course, but my opinion is that Haskell is simply not useful for writing real programs.
It is very much worth learning in order to get comfortable with functional programming. Many useful languages -- Kotlin, Ruby, even Python are incorporating tools from the world of functional programming.
Behond utility, learning Haskell is fun and challenging; mentally stimulating. My mind has been enriched by learning what I have about Haskell.
Tom's Computer Info / tom@mmto.org