Unfortunately I have to agree with your inner voice that there's no perfect language out there.

I'm building my first library in OCaml for a number of great reasons: 1. the type system we all want 2. multicore is here (but in RC) 3. algebraic effects is here (but in basically RC) 4. build system is pretty good after you warm yourself up a bit. i ran into some weird dep issues recently but overcame it by vendoring deps directly.

A hard requirement for me is to be able to generate native executables, and only OCaml / Rust / Swift has this with a more modern type system. If I wasn't so focused on learning in an fp language, I'd use Rust for my needs.

If you asked for a vote, I'd say give 2 weeks for each of your top 3 languages. Opinions and anecdotal experience will always be beaten by personal experience.