I like Kotlin. However, these decisions aren't always simple - and are based on more than the technical merits of the language. Some years ago, my division at

I like Kotlin. However, these decisions aren't always simple - and are based on more than the technical merits of the language. Some years ago, my division at <large company> decreed Scala was the way of the future. All new development was to be done in Scala. We were offered training classes. We formed book clubs. We paired, shared, and opined as we tried really hard to do functional programming correctly. We genuinely tried, and then we gave up. The specific reasons would better suit another post, but it was a grassroots developer-led effort that led us to abandoning Scala. At this point, we have backend code in NodeJS, Scala, GoLang (this is currently a performance-sensitive one-off), and Java. That's a problem for code reuse, tooling reuse, and general maintenance. If we were to write new components in Kotlin, we would be making the problem worse. At this point in time Java is our safe fallback. In the future we may try a different language again, but for now there needs to be a really good reason to add to our tech stack. I suspect most new projects will continue to be Java for quite some time, because we're not going to rewrite all the Scala and NodeJS code "just because". It will slowly get replaced as it stops working, or as we find reasons to replace it other than "it's in a language we don't like". Until then, our polyglot set of codebases is too intimidating and devs are going to resist adding another language to it.