I think it’s your inexperience talking here as programs in both languages here use mostly the same naming conventions and abbreviations, the main difference being that Ocaml is its usual terse and to the point while Rust is well far less terse
To be clear, elegance is important. A language absent of elegance would be a bore to write (cough Java cough). But too much elegance and it can eclipse the legibility of the language. No type annotations is elegant. Is it legible? Not in my opinion. But perhaps it is in yours.
The Ocaml program is mostly matching followed by a chain of operations. It’s far removed from elegance for elegance sake. Meanwhile Rust is handicapped by the machinery it forces you to deal with as a lower level language introducing life time.
Type annotations are a non issue. They are systematically provided in Ocaml in a different file than the code. This header file is not provided here because well it’s a blog post.
But also, the editor plugins don't work on the compiler itself? Why's that? So you can't use Merlin on the OCaml compiler? That doesn't seem great.
And what's with the syntax highlighting being funky? The highlighter appears to think that a lot of these files have unterminated comments or string literals.