OCaml's object/class system is actually pretty good. It isn't used very often in OCaml because most of what OO gives you can be more naturally expressed in other parts of the language, but that doesn't mean that it's bad. In particular, classes are still the best mechanism for open recursion in OCaml, and should be used when that is what is required.
OO in OCaml feels as if the designers thought "we think OO sucks, so let's implement terrible support for OO to get our point across".