You do realize there are plenty of languages out there, and most novel features appeared first in some minor research languages? Like, there is hardly anything original to kotlin on your list, sealed classes have been in scala forever, and are basically just algebraic data types. Data classes are.. data classes, multiline strings is a cool but very basic syntactic sugar available in millions of languages, coroutines have been around, and kotlin’s couroutines are nothing like project loom. The latter is more similar to go’s threads. Switch expressions have been in scala forever, but a pretty basic thing in FP languages.

These aren’t ‘Kotlin features’ they’re just normal language features.

I really struggle to see Kotlin as being part of the debate here. These features are being driven by enterprise Java user pain points. And those people aren’t looking at Kotlin.