OCaml is fantastic, but I avoided it and went with Rust for many projects because it had no multicore story and no green threads for a very long time. But it has that now, and I wish I could go back and start everything over in OCaml.
I've also felt very similar, and adopted Rust for those reasons. Even though I'd still love to have a garbage collected, AOT compiled ML-variant, using OCaml still feels like a step backwards now. OCaml's module system and generics feel clumsy and unintuitive now that I've used Rust's Trait system.