I have never met a single person who has said this, let alone capable of following through.
If you are capable, I am envious of your determination/natural talent. Or alternatively I and every programmer I know are idiots. Actually both seem like possibilities.
Most programmers haven't taken the time to actually learn Haskell.
Haskell only seems hard at first because it incorporates a lot of ideas that other languages do not. For a lot of developers, learning Haskell is a little bit like learning to program from scratch all over again.
In that sense, yes, I guess it's hard, but so was whatever language you learned first.
I find this to be the greatest joy of learning a new paradigm, everything is new and unknown, so even simple things are fun (again).
For example once you have a working program and decide that actually some value could be read/written using a file instead of computed at runtime and the place you use it is 10 levels deep after calling a non-IO function, you've got two choices. Unsafe IO (then why not use it everywhere) or a minor program redesign. Haskell is the only language where I run into this kind of situation. (it's still quite simple despite this)
Have you tried the School of Haskell, it incorporates the minimum viable skills for learning haskell (pulling code apart in the REPL, and understanding type signatures, pattern matches and compiler type check errors)
https://www.fpcomplete.com/school/how-to-use-the-school-of-h...