Ok, so, assuming that all the things he mentioned are just nitpicky, what's the upside of Kotlin over Java 10?
Lots of people would need adequate training, perhaps some new tools and rewrites. There needs to be a serious upside to get a mainstream company to a niche language.
Major thing for Android developers is that the adoption of new Android versions is so slow, we're really stuck with Java 6/7 features. While backend can happily update to Java 15 on their own terms, we're limited by Android OEMs to provide updates to their phones. This is one of the reasons Kotlin is so popular with Android -- you get new Kotlin features when you want to, not when all of your app users buy new hardware (and good luck convincing business people to ditch 10% of the users on old API versions). While we get support for Java 8 (but not 9 or 10) language features via special tool, we still don't have access to Java 8+ APIs.
It's not worth it, Java is getting better and more feature rich that improves programmer productivity. Kotlin is like a cool JavaScript library in the market.