The problem in Android has always been that the framework design is pretty bad in design and technical architecture terms and its evolution over time has made its glaring flaws more obvious and actually made it even messier, rather than the language (Java is fine as languages go and UI stuff only has to run in user-time, so response times of 100ms are fine and bleeding edge performance is not required).
Further, splitting the user base into two languages, by introducing a new language that is not used anywhere else (hence you're not going to find Kotlin programmers from outside Android development whilst you will find plenty of Java programmers) is one of the stupidest technical architecture decisions I've seen, and I've been in the industry for over 2 decades.
Last but not least, the gains from the small programming-time efficiency advantages of Kotlin over Java are a drop in the ocean next to the losses due to the Android Framework itself being badly designed (something as simple as not having functions in different core classes that do the same thing named the same).
Even for programmers going for Kotlin is a less than wise career move: as an Android-only language those who specialize in it are locking themselves into programming for Android only and have fewer career options - hands up anybody who expects to still be programming Android in 10 years time! The great thing of generic languages is that there are a lot of lateral career moves you can make without the high likelihood of failure that comes from hiring managers naturaly prefering people with several years of experience in the programming language used in their projects over people who say "I've mainly done Kotlin but I can learn that easilly".
What many years of experience in the industry tells me is that you don't want your career to hang on the ficklness of a vendor, any vendor, especially the likes of Google who will drop massivelly hyped systems with tons of 3rd party investment whenever they feel like: just ask everybody who invested in developing for Stadia.