Oh common. First of all they don't have JVM, they have own runtime, second, if you talking about dropping support for JVM Class format for some reason, it would make it completely incompatible with current code with no real reason. Second, assuming that it would l somehow dramatically improve performance by itself is at least naive assumption. Third, they focus on ART performance, which of course target wide range of common applications, and swift has classes for sure, if you talking about SwiftUI it super funny, because for example Compose not only avoid classes, but actually uses just compoasable functions that do not create tree of components for diffs (like shadow dom or SwiftUI structs), which, at least in theory is actually more performant approach than in SwiftUI
And finally, If you think that ART is much slower and desperately broken by definition, you are not limited by ART, you can compile exactly the same code (even swift) to native binaries for ARM processors if for your use case it works better
Also, because we are in gamedev channel I really don't understand all this ranting about ART or Swift performance, because most of game engines are written using C/C++ (at least core) and it's true for Android, iOS or desktop, again, just because for core components of high performant code you just should use lower level tools, same way as sometimes instead of C/C++ native development goes to assembly level, not because it's better in general, but because you want to optimize some very specific code, same way as sometimes JVM libraries use sun.misc.Unsafe