I'm surprised you feel Kotlin is incomphrensible though, it definitely can be written that way because it has features that allow for extreme terseness.
I think there is a minimal set of things you need to learn over Java for Kotlin to make sense, nullability operators, block passing syntax and the differences in OOP (inheritance/interfaces are slightly different, classes are closed by default, companion objects replace static methods).
So yeah. Kotlin is strictly larger than Java so it takes longer to learn all of it.
That said because of the look and feel of Kotlin it's more accessible to developers of Ruby/Python/JS/Typescript. This tradeoff is personally worth it for me.
Not because I care that much, I can just as easily use Java. However it's -very- difficult in modern times to convince my team and company to use Java when there is hipster options like Typescript taking all the air out of the room. Kotlin competes in the same area but provides the same battle tested runtime and excelent libraries, it's almost like a compromise between the new age and the old age.
This is why it's such a great language for me in particular but I realize not everyone is in the same boat.
But then, I've seen some shit Java too.
That's not my truth.
I tried it, after not doing "real" programming for a while, and found it the most obfuscated, incomprehensible language I've ever run into. What new concepts are there in Kotlin that justify it?
"Expressiveness" sounds toxic to me - along the lines of "facilitates a personal idiom that makes your code impossible to understand and you irreplaceable".
After several days trying to do the simplest form of asynchronous processing in an "hello world" Android app, I switched back to Java, and everything made sense again.
I also wrote a small program in C# and that too was just as easy as I recall from ~10 years ago.