Does a junior developer understand the core abstraction of a given project written in any language? Chances are the answer is no. Haskell just expresses that inside the language, while other languages tend to rely on design patterns, or just simply distributing the logic between many parts, which are arguably more error prone.

But for all practical matter, they can better write a single isolated case because it has to abide by stricter typing rules, instead of only conventions that supposed to he upheld.

Yeah, better than in other languages I'd argue, as the meaning of the code is not obscured as much. This becomes especially (but not exclusively) clear with clash vs. VHDL/Verilog.

You have to actually know Haskell first, obviously.

I also want to add: That was actually the point of my comment. "Applicative functors" may sound scary as a name, but the concept really does help in keeping things readable.