The likes of TypeScript, Babel and JSX are providing a simple source-to-source transformation that leaves the structure untouched, broadly just changing the exact syntax employed. (I exclude any transformation of async code to not use async/await syntax; that one is a more involved transformation.)
Svelte is not like that. It’s unequivocally a compiler, doing much more involved transformations. If reactivity becomes involved in your debugging efforts, it can indeed be harder to pin down than in plain old JavaScript—depending on how that JavaScript was written, of course.
Compared with the likes of React? I have no real idea, I’ve never used React seriously. If the issue gets involved with the depths of React or Svelte, remember that there’s a lot less of Svelte, which may make it easier to debug. But for some of the sorts of problems that could occur, I would expect React to be easier to debug, because the bit that’s your code is essentially just plain JavaScript.
For myself, I choose to use Svelte.