Are you sure you're not confusing Kotlin with Scala?
> For example, Kotlin has null safety and it lets you write code using errors-as-values style "either" types - but it has two completely separate syntaxes for these things, and so it's impossible to interoperate or reuse code between those two approaches
And that is a problem how? Stick to one style.
> In practice Kotlin codebases still use magical incomprehensible reflection (Spring Boot)
Switching an API from "a result or nothing" to "a result or an error message" happens all the time, and switching in the other direction is only slightly less frequent. And of course most programs have some APIs where one is appropriate and some where the other is. So consistency is valuable.
Are you sure you're not confusing Kotlin with Scala?
> For example, Kotlin has null safety and it lets you write code using errors-as-values style "either" types - but it has two completely separate syntaxes for these things, and so it's impossible to interoperate or reuse code between those two approaches
And that is a problem how? Stick to one style.
> In practice Kotlin codebases still use magical incomprehensible reflection (Spring Boot)
https://github.com/spring-projects-experimental/spring-fu/tr...
> and magical compile-time manipulation (Kapt)
There's nothing magical about it.