Honestly I doubt Ocaml will ever be truly mainstream, for the following reasons.
A. The community’s, don’t be a pussy, read the source or api docs, and if you’re still stuck ask mentality.
B. Most developers, want magic, so they are more inclined to prefer haskell type classes over modules.
C. It leaves a lot up to the developer, so a lot of build tools, a lot of small libraries.
D. The intended audience for most of the ecosystem, are systems programmers, not application programmers, before anyone tries to dispute this claim, read the package list on OPAM.
E. Popularity of Go, they occupy many of the same spaces, Go is even easier to learn than python, and has a fuckton of libraries, I ended up using Ocaml as a replacement for Go, but most people tend to value ease over simplicity.
Ironically A-D are the major reasons why I love Ocaml.