I don't think they said they didn't believe. They were just asking for actual arguments, which seems fair to me.
As for Cabal hell, doesn't Stack [1] help with that? To be honest, I'm unhappy with dependency managers in most languages: Maven, the things Golang uses, or Python, or NPM (shudder!), etc. This really doesn't seem like a solved problem :(
Cabal hell is a solved problem these days. Solved three different competing ways --- nix, cabal new-build, Stack --- where ideally there'd just be one, but not the issue it was five years ago.
That doesn't mean dependency management is always easy. It's a hard problem in any language. But you won't find yourself in an inconsistent state that requires blowing away your installation if you use one of those three approaches.
