The base looks similar (space is function call, static types inference, currying, '->' for function definition etc.) because the common ancestor for haskell, o'caml, erlang and various others is ML, another language.

This is the same kind of relation between C, java and C#, the basic type system and grammar are cousin.

I won't answer to the "static typing is inflexible", but you should check the type system itself, and its genericity system and modularity system.