Can you give a concrete example of the kind of code you'd like to write that you can't write in Typescript?

Types absolutely are a first class citizen in TypeScript. Especially coming from Go, which doesn't even support generics, Typescript is really quite powerful. It even has support for ADTs via discriminated unions, which gives you the same power of enums with associated types that you'd get in Rust/Swift.

Is it possible the reason you feel like Typescript doesn't have Types as a first class citizen is because it leverages structural typing rather than nominal typing?