>There are some cases when null can be missed by the Kotlin compiler

Example, please, or it doesn't exist. The only case if when interacting with Java code

>Also, devs often abuse `!!` with obvious results

So? People using unsafe Rust code don't void the promise of Rust being safe

>the use of Option in Java along with the convention to not use null in class API works very well, definitely not worse than Kotlin's "null-safety"

Along with the convention. You can stop right there.