You don't need RTTI to deserialize data in a clean way. What you need is return-type polymorphism. Haskell has this and it makes writing serializers and deserializers symmetric and totally painless.
Return type polymorphism and inheritance doesn't mix very well.
Swift got into this mess early in it's lifecycle and it's type checking is still more expensive than the rest of the compiler combined, and unpredictable on top of that.
C++ has both return type polymorphism and inheritance. What it doesn't have is the kind of type inference that Haskell has. Its type inference is very limited.
