Kotlin has JVM, Native and JS targets. And as a language it is much better than Haxe, I would be careful about such statements.
(I have no opinion on the argument, never having used either language. I just found the rhetoric funny.)
You cannot just pick a random Java library, even if pure logic code, one of the Kotlin FFI selling points and use it with Kotlin/Native, if it wasn't originally written with Kotlin/Native memory model in mind.
In practice, there are things about Haxe I miss in Kotlin, but also things about Kotlin I miss in Haxe. Just to name a few examples:
- I'm missing Haxe's pattern matching and macros in Kotlin
- I'm missing Kotlin's level of IDE support and robust null safety (with ?: and ?. operators) in Haxe
(Haxe does have experimental opt-in null safety, but it doesn't seem production-ready yet)