> Yes, I know hardly anyone uses Swing anymore.
Actually, Swing is the GUI toolkit used by IntelliJ IDEA, one of the few if not the only commercially successful and kick-ass Java desktop app(s).
The only real problem with Swing is that there was never a version 2. If it had been separated from AWT, updated some of the APIs and given a modern look-and-feel, it would still be relevant today. JavaFX is nice, but it broke too many conventions.
And, of course, Oracle or OpenJDK (or someone) needed to invest in a browser port of the JVM, which is totally possible these days.
Take a look at FlatLAF:
https://github.com/JFormDesigner/FlatLaf
They have done a great job bringing a modern appearance to the Swing components.