Ocaml does tend to be more verbose than Haskell - it's just the nature of the language syntax. E.g., in Ocaml, one says (fun x -> x+1) vs (\x -> x+1). Similarly, ocaml is cursed by the excessive "in"'s that accompany let bindings. "Let .. in let .. in let ...". That can get annoying.

Interestingly, I had the opposite experience with a commercial compiler project. Haskell's syntactic cleverness (monadic syntax, combinator libraries, etc..) eventually got in the way - it became very difficult to understand what a single line of code actually meant since one had to mentally unpack layers of type abstractions. Migrating to ocaml, the verbosity eventually was more tolerable than the opacity of the equivalent Haskell code once the compiler got sufficiently complex.

My experience may vary from yours. I've been doing Haskell/Ocaml in production for many years, so the pain points I've adapted to are likely different than one working on toy compilers or weekend projects. And no, category theory exposure is not and never has been necessary for understanding Haskell or FP unless one is a PL researcher (and even then, only a subset of PL researchers are concerned with those areas). And one can be quite productive and prolific in Haskell without a deep understanding of monads and monad transformers - the blogosphere has given you the wrong impression if you believe otherwise.