In python or typescript, the most popular languages in the world, it offers no runtime safety.

Even in languages like Haskell, "safety" is an illusion. You might create a NumberGreaterThanFive type with smart constructors but that doesn't stop another dev from exporting and abusing the plain constructor somewhere else.

For the most part it's fine to assume the names of types are accurate, but for safety critical operations it absolutely makes sense to revalidate inputs.

> that doesn't stop another dev from exporting and abusing the plain constructor somewhere else.

That seems like a pretty unfair constraint. Yes, you can deliberately circumvent safeguards and you can deliberately write bad code. That doesn't mean those language features are bad.