I agree. OCaml too. I think there are several factors that lead to it being very difficult to read other people’s code:

• Currying and lack of syntax in general means you have to be a human parser for basic things like “which part of the text is a function name? which bits are arguments?”. Often it’s impossible to tell without looking up the function definitions.
• The functional style - while generally great - also makes it very tempting for people to write enormous heavily nested functions where the control flow is hard to follow. You sometimes get assignment expressions that are hundreds of lines long.
• Haskel & OCaml feature global type inference. Programmers often omit explicit type annotations which very often means that function types are inferred as generic. This means you lose several huge benefits from static types. For example you can no longer look up the types that will actually be passed into the function, and inferring the authors intent is much harder. It also makes error messages way more confusing.
• I don’t know why but Haskel and OCaml programmers love stupidly short identifiers.
• They also abhor comments.