1. TypeScript is just a modern expressive strutural typing system on top of JavaScript, not a full new language.
2. Modern JavaScript (es2017) is not our old JavaScript, the language matured very well. Not perfect, no language it, but as good as it get for a scripting language, and TypeScript has a lot of structure while keeping its flexiblity.
3. JS/TS really enable a Functional First, OO as needed programming style, which can greatly reduce boilerplate code and API code complexity, which in turn makes the code scale better.
Note: I have been doing Java for the last 20 years, building big enterprise Java app for a living for the last 10 years, and right now, I would say that Modern JS / TypeScript and all of its benefit, offer a better productivity environment for big app development, that traditional Java. We just ported one of our client's Java backend, 40% less code, better typed, and better scale (as most node libs are nio/async in nature)