Although my opinion is exactly the same, I do not think they had an alternative when they started working on Flutter. Kotlin was not a thing yet and even now compilation speed has room to improve, I think it is a bit too late now and they do not have plans to introduce alternatives. For example, they started from Skia which has bindings for other languages, but the new impeller was developed purely for Dart. And this is concerning living with no room for alternatives withing the Flutter ecosystem.