Given that every other version of applications/oses changes the definition of what "native" looks like... I don't know that it's a huge problem...

Beyond that is the fact that Swing was fugly everywhere, and bootstrap looks decent everywhere.

Well, JavaFX’ styles look beautiful everywhere, too. (And it even uses decent XML and JS for styling and interaction).

I just argued against the parent poster, who said Java was different than browsers, because you could not make native UI.

Which you actually can very easily.