However, it isn't free. Type theory is a kind of math that most people have very little exposure to, so there's going to be a lot of work in order to start becoming proficient.
Additionally, there's more than one type of type theory. Are you using a system F like system? Are you going to have sub-typing? Is it going to be structural sub-typing? Maybe you want row polymorphism. Is there going to be a kind system? What about higher order poly kinds? Dependent typing? Intensional or extensional?
Additionally, there's more than one type of implementation of these type systems. Ocaml functors ... is it a generative or applicative functor? Haskell ... are you using gadts, functional dependencies, or type families?
In the end I think that type systems will eventually be able to get you a completely typed experience that feels exactly like a completely dynamic experience, but with compile and design time checks that always make you feel good about the experience. However, I don't think we are quite there yet and I don't think you can expect everyone to be able to take the time to get sufficiently familiar with an arbitrary type system in order to be productive with it.