Interestingly I have the exact opposite perspective. Writing imperative or OOP code requires me to be excessively disciplined. It is extremely easy to build un-maintainable spaghetti. There is a whole cottage industry of methods for your discipline of choice: Clean, SOLID, TDD, etc. All these disciplines seem to boil down to the same systemic result, push effects to the edges of you program so you can more easily test, evolve and maintain. Functional programming (of the typed variety) tends to allow me to write garbage code, that is testable and can be easily evolved and maintained because the paradigm encourages me to be a good actor.
I've refactored production code in imperative languages and typed functional languages and only one of them allowed me to make HUGE sweeping changes with ease and high confidence.
I'm not a big OOP fan, but I'm pretty sure Clean and SOLID are principles (or sets of principles), while TDD alone is a practice. I'm also not very familiar with Clean or SOLID, but I'm pretty sure they apply to Haskell as well, and I would expect that Haskell enthusiasts would ordinarily boast that Haskell allows (or encourages) them to write code that is more SOLID with less effort than other languages.
My criticism of Haskell is that there tends to be an obsession with writing the most SOLID/DRY/etc code possible at the expense of productivity. It's a code golf / ego culture.
Yes, this is cultural and not "built into the language" (quotes because I doubt there's a clear distinction between a programming language's culture and the language itself, but that's a debate for another time), but you can't unplug from the culture, because you need the ecosystem to solve any nontrivial problem (so you still have to interface with overly clever code).
Further, even if you could unplug from the culture (perhaps by writing everything in-house under your own improved culture), there are still no 'rails' that encourage naive, flat-footed, dumb code, and that's the kind of code you want 99% of the time. As far as I'm aware, there isn't even a clear standard for writing clear, naive code in Haskell.