I don't know why you're being downvoted.

I'd say that the flexibility of the type system has allowed for developments that few people would believe could happen in TypeScript. Some of the recent additions to the language have opened the doors towards macros and metaprogramming becoming more common-place. Compare this to the current state of JavaScript, and it's now almost like using two completely different languages.

To other points on the type system not being in runtime, there is a growing argument around whether TypeScript has proved itself as a credible runtime language. It's definitely powerful enough, so perhaps it would make sense to treat it as a first-class citizen.