No, you still need to deal directly with JS even with a transpiler like Dart or whatever other language you want to use. When things go wrong, and they will, you'll need to deal with the JS errors. When you're trying to debug or even call out to JS APIs, you better be intimately familiar with how your transpiler interops with JS, otherwise you're kinda screwed.

Dart hasn’t been much better in my experience, but you have reminded me to revisit Kotlin/JS!

Does anyone use Dart without Flutter? I've never seen it used separately.