I'll take your word for it then, since I have seen similar opinions expressed before, but when you say "serious" what particular qualities are you thinking about?
What's more Haskell specific is recognizing many problems can be solved easier when seen through the lens of parsers, interpreters and/or compilers.
Haskell's and the whole ML family of languages are great at writing parsers etc. In fact they were originally invented for implementing other languages.
I meant that solving a problem in Haskell can often mean eg writing something a bit like a parser.