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In my personal opinion, Kotlin is a joy to code with. And since it's 100% compatible with the JVM and essentially IS (much much) prettier Java, why not use/promote it more? I don't see why it should still be thought of as just "the Android programming language".
If you're an experienced developer, I don't think there's a heavy lift to understand how Java is translated to Kotlin. It might be worth the "downtime" overall. Thoughts?