Yes, it assumes some knowledge of the language. But imagine if every article about, say, Ruby, had to explain things in a way that someone who'd only ever seen C would understand? Authors would be hamstrung, unable to talk about things at any level other than the most elementary.

If you're going to talk about the power of a language you have to allow the use of language that talks about that power. To talk about what you can do in Haskell beyond toy problems you need to allow people to use more than just toy language.

If readers aren't willing to do any work, its tough to help them learn anything new.

Author here: the concept of `Applicative`s is unique to Haskell and has no parallel in other programming languages. This makes the post difficult to write to a broad audience. Instead, I just tried to show the neat things you could do with `Applicative`s to try to entice people to learn more about them.

That's definitely a valid criticism of the article, but not really an explanation for the OP's post AFAICT.

I don't think a beginner would be in a position to judge what is 'jargon' and what is essential terminology.