Modeling your domain using types and checking your types are two different things.
Could you explain where you think the Elixir type system falls short for modeling domains? Your post only gives examples of problems with type checking.
Elixir doesn't have any concept of real tagged unions or sum types. Modelling is intimately connected to checking because when we change something (as we are wont to do) we want to have that change bubble out into the rest of the system safely. This just isn't reliable at all in Elixir.
The most potent data modelling tool you have in Elixir is a `struct`, which is just a `Map` with `atom`s for keys. You can then associate this map with an ad-hoc `atom` tag in some return value if you want, and that's as far as we can go.
Modelling behavior in Elixir is easier and better, with processes, but having absolutely zero guarantee that what you're doing makes sense when it comes to data hierarchies and composition is just not useful when trying to outline what data represent and how it can be represented.
Could you explain where you think the Elixir type system falls short for modeling domains? Your post only gives examples of problems with type checking.