I have seen many systems that were overly complicated because the developers couldn’t keep it all in their head. It led instead to poorly designed modularity along boundaries selected to be small enough that they could keep it in their heads, to the detriment of both efficiency and maintainability.
Being able to see across it at scale is what exposes elegant reductions to something simpler, which enhances maintainability. It is how you end up with the commits that delete a thousand lines of code.
Plus people with intellectual limitations are not immune to their own variant of over engineering. They will at times pile up useless layers and intermediate steps thinking they created something incredible or replicated badly something they saw on YouTube the week before.
(Like you, I of course immediately thought about the famous Artur Whitney's page of impenetrable C.)
The genius of J (and APL) is exactly in the simplicity of the language, where a single character denotes a whole well-defined operation on arrays which might take a page of Fortran code, and these operations are orthogonal, and useful for practical purposes.