"fatter, compiler is slower, code completion is slow as hell" - if that's all you want out of your programming language, then Java is probably a good choice for you.

For others that value the things that Kotlin brings over Java (even modern Java), and for the ways in which it delivers a simpler experience than Scala - I think it's a pragmatic and sensible decision.

I wonder if that confusion is due to the fact that you haven't yet wrapped your head around the fact that extension functions are "just" syntactic sugar for static functions. The implicit "this" becomes the the first parameter of the static function and function parameters can be null. Now you might ask "why not use static (/first class) functions then? Because those "feel" like less ideomatic to use then extension functions or methods that are defined on the object (hirachy) itself. But understanding why the extension type can be nullable is not the same is using it on nullable types. I restrict my extension functions to non-nullable types most of the time as well. The best exception to this preference -just to see where it makes sense- is the build-in function [toString](https://kotlinlang.org/api/core/kotlin-stdlib/kotlin/to-stri...), since you want it to return "null" if you invoke it on null.