Beginners face the following problems: there's multiple standard libraries, many documents are barely more than type signatures, and data structures aren't printable by default. Experts also face the problem of a very tiny library ecosystem, and tooling that's often a decade behind more mainstream languages (proper gdb support when?). OCaml added multicore support recently, but now there is the whole Eio/Lwt/Async thing.
I used to be a language nerd long ago. Many a fine hour spent on LtU. But ultimately, the ecosystem's size dwarfs the importance of the language itself. I'm sympathetic, since I'm a Common Lisp man, but I don't kid myself either: Common Lisp isn't (e.g.) Rust. I like hacking with a relic of the past, and that's okay too.