Scalaz is widely used and widely panned. Even though I'm a haskell and purescript programmer that prefers to write <$> and >>=, I find Scala's approach frustrating and hard to read. Especially as type lambdas stack up.
I'm just saying; the impression exists for a reason and the reason is a popular and well-known library.
But pointing at Scalaz is a bit ridiculous. It's a known test library for trying things out and basically not allowed in any Scala codebase I've been working on.