1. Let's create a super advanced type inference system so that you can write Haskell like a dynamic language but have it be static.
2. Oops, now when you make a mistake, it propagates through your program and causes a type error somewhere completely different.
3. New code style rule: you may omit type signatures on local functions, but always place them on top-level functions so that they serve as a barrier to incorrect type inferences.
Trying to write untyped dynamic code in a statically typed language thus just results in frustration, those languages were made to work statically and to throw a lot of type errors, they are horrible as dynamic languages.
This isn't true at all. I write a lot of python and I don't think I've ever had a duck-typing happy coincidence that wasn't an error. No it's exactly that I'm only depending on the aspect of the type that I need at the call/use site (so I can update types while maintaining those contracts and I don't need to update any signatures anywhere).