https://github.com/scalaz/scalaz/blob/series/7.3.x/tests/src...
It is a mystery.
I'm not the biggest fan of Scala, but for me it's more that it reminds me of Java than the functional constructs.
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.
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.
I'm all with you here. I prefer Haskell and OCaml every time over Scala.
Scala is a super approachable language, without any (that I can think of) strange operators in the stdlib. You could make a case for Cats, I guess, but writing purely functional Scala isn't necessary at all, and is something you can approach when or if you feel comfortable to do so.