* Windows support is mediocre due to decades of not supporting it at all.
* OPAM is a nightmare. Surprisingly buggy and extremely confusing. We're not talking Pip levels of badness but it's nowhere near as good as Rust, Zig or Go's equivalents.
* A silly obsession with linked lists. Ok I understand why but it's still annoying.
* Ocamlfmt thinks it is writing an essay, and generally makes things less readable IMO.
* The syntax is not easy to read. They threw away all the useful punctuation that help you visually parse code.
* Tiny community.
* Very spartan documentation. Examples are very rare.
* Global type inference is definitely worse than Rust's local approach because it makes errors much worse, and makes the code harder to understand.
* Native int type is 63 bits.
I haven't even done much OCaml but it's definitely got enough issues that I strongly prefer Rust. Just the community size is reason enough really.
That said, it's still way better than Python, Ruby, PHP, Java, JavaScript and Perl. Those are kind of the Z-tier languages though so I guess that's not saying much.
If it was a choice between OCaml and Go, Swift, C#, Dart... then it wouldn't be a slam dunk either way. Unless you wanted Windows support and then OCaml is a crazy choice.
I used OCaml extensively for a few years, around the time of OCaml 3 and OCaml 4, and I can add a few cents to this discussion.
Some of the points listed here can be considered a matter of taste or opinion, some are indeed pain points, and some are implementation details.
OCaml as a whole is hard to directly compare with most other languages you mentioned above as "better" or "worse". It both suffers and benefits from being an academic/research project not directly in control of a larger corporation.
As a language, IMHO, it is miles ahead of mostly all the languages mentioned above. It recently adopted a novel mechanism for modeling concurrency called algebraic effects, together with state-of-art multi-core support. This not only abstracts away several features that are usually hardcoded on most languages but puts it on another level as a language and abstraction capability. There are other toy languages that implement similar mechanisms or part of this, but none with the adoption level of OCaml.
However, since it does not have the same amount of resources and adoption, progress sometimes is slower that one would expect. Documentation can be sparse, community is smaller, etc.
Regarding OCaml on Windows, I myself used it exactly 20 years ago. It not only has one implementation, but three. There are some tradeoffs and support is not at the same level as Linux but it's still there, and I wouldn't call it mediocre:
You might find it harder to find libraries, for sure. I have not checked the situation recently, though given the smaller community that is likely still the case.
As a tongue-in-cheek comment, I could definitely say "OCaml is certainly not a good language - not as bad as most of all the others though".
