The code it generates leaves a lot to be desired. It's highly non-idiomatic, and has the marks of a computer-generated structure all over it. This being said, it certainly facilitates the transition from Java to Kotlin as it makes for a convenient learning tool (used on small portions of code).
The transition to Swift has accelerated in the past year. Might be because of SwiftUI or because it’s now mature.
ABI stability. You don't need to ship the whole runtime with it anymore. Though if you want a framework that works nice with both languages and older versions Objective-C is still better.