There are other ways of making refactoring easy. I'm not trying to dismiss a powerful type system - which is a great help indeed - but pervasive unit tests and contracts work as well. Linters are a nice addition, and even gradual typing like in Erlang with Dialyzer is much better than nothing. The point being: problems solved by type systems are being solved with other tools, too. I don't want to argue about how well these tools work, because all of them (including static type systems) have relative strengths and weaknesses; it's just unfair to present refactorings or correctness guarantees as benefits reserved for type systems alone.