Pick a language that you love. That will probably happen to be something not very mainstream. All not-very-mainstream languages suffer from the lack of good, quality libraries to one degree or another.
Fix it. Since you mentioned OCaml, I assume you like it. I suggest you look at Python libraries (very mature bunch) and port something you like over to OCaml.
Fix it. Since you mentioned OCaml, I assume you like it. I suggest you look at Python libraries (very mature bunch) and port something you like over to OCaml.