Using "Maybe" as a positive example of what Haskell can do isn't right. Say you have a function with input of type A and output of type B, written (A -> B). The problem with Maybe ("option" types) then is that if you have a function, in production use, of type (X -> Maybe Y), you can't "weaken your assumptions for the input and strengthen your promises for the output" (which would be an improvement) and rewrite it to the type (Maybe X -> Y). Because then you would have to modify all the code which already uses the function. Since "A" and "Maybe A" are incompatible types. Which is illogical.
Several other null-safe languages solve this correctly by allowing disjunctions of types (often called unions, though countless other type related things are also called unions). They have a type operator "|" (or) and the function type (X -> Y|Null) can be improved by rewriting the function to (X|Null -> Y). Code outside the function doesn't have to be changed: Accepting X or Null implies accepting X, and returning Y implies returning Y or Null.
Several other null-safe languages solve this correctly by allowing disjunctions of types (often called unions, though countless other type related things are also called unions). They have a type operator "|" (or) and the function type (X -> Y|Null) can be improved by rewriting the function to (X|Null -> Y). Code outside the function doesn't have to be changed: Accepting X or Null implies accepting X, and returning Y implies returning Y or Null.