Just because there are cases where over-validation (email address being the primary example) can be a problem doesn't mean that _no_ type validation is useful.

Just because there are cases where over-validation (email address being the primary example) can be a problem doesn't mean that _no_ type validation is useful. There are many, many places where validation-beyond-primitives is useful, or even just types that need actions taken on them before they can be used in place of another type. One simple one is "non-negative integers", not commonly provided as a primitive type but _very_ common to need to be able enforce. Complex numbers are another. Normal strings vs HTML strings (need to be properly handled before they can be output to a front end). The list is endless, and custom types can provide a _lot_ of safety.