How much time have spent with TypeScript? I'm sincerely asking, because the answer is either "not much" or you didn't do a lot of research. You've misunderstood (or chosen not to investigate) some very fundamental things about TypeScript.
> function add(x: number, y: number): number {...}
You don't have to do this in TypeScript. In fact, you can use TypeScript without transpiling your code and without creating any types yourself.
Why would you do that? Because a lot of open-source libraries now come with types included, so you get type-checking for those APIs essentially for free.
> I'd just use Java
Java has a nominal type system. If you want a new type, you have to create it.
TypeScript has structural typing with type inference. That means you "just code" and the compiler will pick up your types if you go. If you write inconsistent code, it'll warn you. If you want to refactor a type, you now have enough metadata for your code to do that confidently.
> When is Typescript going to have its own version of the V8 engine and just leave JavaScript out of it?
Microsoft has had its own V8 competitor since around the time TypeScript was released[1]. They literally can't leave JavaScript out of TypeScript because every JavaScript program is a valid TypeScript program. TypeScript is a superset of Javascript. Other than the type system, it does not introduce any new features that are not on the EcmaScript roadmap.
> harkens back to the classic Microsoft Embrace, Extend, Extinguish strategy
Uh, no, it doesn't, because they have (A) open-sourced all of it, and (B) they haven't extinguished anything. Even if they did, there are massive numbers of people, including Google, who use TypeScript in production and would keep it going. There is no practical way to extinguish anymore.
In fact, all of their behavior (e.g. with the .NET ecosystem) suggests that Microsoft doesn't do those things anymore.
1. https://en.wikipedia.org/wiki/Chakra_(JavaScript_engine)