Yes that's true, but there's effort to consider on both sides of design decisions like those TypeScript has made. Much of the compile time behaviour comes from the decision for TypeScript to be incremental on top of JavaScript. That allows you to start getting the benefit of TS without the effort of having to rewrite your entire codebase, for example. Having used TS for many years now I feel that the balance it strikes is incredibly productive. Maybe for other folks/projects the tradeoff is different - but for me I would hate going back to plain JS, and there's no alternative available with such tight integration with the rest of the web ecosystem.