Don’t use Kotlin? Or just deal with the lack of language support.

Or use it, and accept that the language support is about as good as it usually is for Emacs? Emacs has never had the full range of features an IDE has.

That's a weird thing to say when for example Emacs+SLIME has had everything you wanted from a Lisp IDE for more than a decade.

There's literally no reason for not having full IDE experience in Emacs.

That's another reason why I don't like programming languages that need a specialized IDE. PLs should be simple. Not being able to use a language efficiently in any editor of your choice is like working with a programming language that needs specialized proprietary hardware to compile.