It's interesting/refreshing to see non-Java shop picking up a JVM-based language for their new back-ends. I don't think it's bad. Kotlin is a fine language.

The language choice is not only about simple pros/cons but more about the people who use it. I thought people in non-JVM land have some physiological distance from JVM land, but probably I'm too ill-informed by HN pop culture.

(An unsolicited advice: Stay away from Guice. It's not too late. There are better options like Dagger and Koin.)