I lost confidence in Haskell's ability to let me write something one way and safely refactor it later, when I found out that you can't use a ton of the algorithmic functions in the standard library because they do things all wrong.
Other than strings desperately needing to be purged from the library, what are you talking about?
Haskell has some really solid standard libraries, and it's extended library set has some of the most sophisticated algorithms packages in the world.
If you want to do that sort of thing with Haskell, I would suggest switching to the numeric prelude [0]
[1] https://stackoverflow.com/questions/5892653/whats-so-bad-abo...
I also don't think you need Conduit or Pipes or any other performance destroying free Monad libraries to deal with it. My hot take: Conduit is in fact awful and radically overused and multiple superior options exist.
Not counting obscure special-purpose langs like Coq.