Conversely, the Ocaml module system is powerful enough to do all the things you had want to do with Haskell except the Ocaml module system is nice to use.

Anyway, the issue has nothing to do with relative powerfulness. The issue is that the Haskell community encourages practices which lead to unreadable code: lot of new operators, point-free, fancy abstraction. Meanwhile, the Ocaml community was always very different with a general dislike of overly fancy things when they were not unavoidable.