It's extremely useful if your distribution platform is the web. However, I find it much more valuable as a type checker than a compiler. I use TypeScript extensively (in several projects) for defining schemas types.

For example, in the Breaka Club (https://breaka.club/) editor, which is not presently exposed to kids yet, we define behaviors for characters, props, mosaics (terrain tiles) and items in JSON. But the JSON has type checking and real-time completion as you type. Not naive property auto-suggestion, we have effect types and they're context aware in that you can refer to targets introduced higher in parent constructs of the JSON — and they're fully type checked. If you refer to a target that does not exist in a context, it won't validate and you cannot save the schema.

We use tsgo for development, but the editor (runtime schema validation) is presently stuck on TypeScript 6 because there's no WASM support.

Now, is it nutty that we're using TypeScript for JSON validation? A little. But it's extremely powerful. We're going far beyond what's capable with Zod or ArkType.