Data classes vs value-based clasess

You will have to wait for a long time. As far as I understand, project Valhalla partially breaks the bytecode, so it will be a very long time before Java community will accept that.
If there is one bad thing about Java ecosystem, it is that any new good things take an insane amount time to take place (Java 9 was delayed for what? two years? And what about Lambdas on Android?).