Nullable types, module level functions, context receivers, nicer type signatures for functions, a better standard library (e.g map works directly on lists without the stream.map crap)

Personally, these features are not something I feel like I would constantly be missing. I don't constantly feel like I'm missing them after switching from JavaScript, at least for not having to call .stream(), context receivers (which Java provides with ScopedValue), or signatures for functions.

I'll give you nullable types, though I personally don't struggle with null at all.