I don't think TypeScript is an example of what people would call a "properly expressive type system". Sure, it is very expressive, but it is made to cover all the gaps JavaScript as a language has in a generally type safe manner, and this calls for an EXTREMELY complex and open type system, much more than most languages would ever have, so I don't think this is really appliable as an example. The gap between maintainable code and unmaintainable one sits between the chair and the screen, not in the type system of the language the person is using, the language merely makes that person more or less able to encode more things in specific places that can become unmaintenable (and anecdotally, most unmaintenable code I know don't even use complex type system features, it's just plain old messy state mutating things scatered all around).