Why is Java not considered as a cross-platform solution?

Java on the desktop died because it didn't provide a native enough look and feel and it performed too slowly. Now we just don't care about look and feel and pretend every user has 16GB of RAM like the developer machines do.

Java on the desktop died because most developers were too lazy to learn how to use Swing properly, while writing everything on the UI thread.

Example of a properly done Swing app? Not trolling, genuinely curious to see what that looks like (code + result). I also assumed it was because they perform terribly and look non-native.

jEdit, IIRC, was often mentioned as a properly written java GUI app, I think it's Swing, but I might be wrong.

EDIT: IDEA code is apparently open https://github.com/JetBrains/intellij-community