> Kotlin as a platform is not mature enough to deserve the same qualification. With (1) a lot of Java backend projects migrating to Kotlin (let's be negative and assume 20%); (2) all of Android running Kotlin, which is around 80% of the world's mobile phones; (3) the world's best IDE authors building features and improving Kotlin; (4) the language being almost 13 years old at this point; and (5) Kotlin being 100% compatible with Java in both directions, I wonder what additional maturity would you be looking for. Can you point to a specific problem?

I mean, of course, Java has been here since forever and we've made careers out of programming for JVM. I'm wondering if you are referring to a specific maturity issue, or just want to highlight that Java was here for longer... if it's the latter, I don't think it can be a valid argument against Kotlin or in favor of Java.