What's impressive is that they brought this experience to cross platform mobile. Reminds me of Guy Steele's quote about Java bringing the mainstream halfway to lisp but people could only complain.
It is so impressive that now other platforms are adding it, thus proving the point that Dart is not a special snowflake.
What Java brought, we already had in the form of Eiffel, Oberon, Modula-3, Smalltalk, Component Pascal, Dylan, they just suffered from not having Sun's budget offering a compiler and training materials for free.
Now they are trying to bolt into Java, features that some of those languages already had, but Java 1.0 ditched them like value types, AOT compilation to native code and proper generics.
I am betting that Dart will never have any relevant market share besides being the Flutter's language.
Android team is betting on Kotlin/Native and Jetpack Composer, so lets see who will win the internal politics.