This article seems quite off. First, it conflates browser and desktop. Yes, applets died an early and deserved death. That is different from what happened with desktop apps.

A univeral GUI (e.g. Swing) was wrong-headed. I don't actually know what happened after people moved away from Swing. But even in the time range TFA discusses, Intellij IDEA, an IDE written in Java, was a success. It has always been multi-platform, and never had worse than acceptable performance in my experience. It has grown into a large suite of products, and I think it is widely considered to be the best IDE, for pretty much any language you can name, by a wide margin.

Java has become the new COBOL -- the language for business applications, which means backend development. But the continuing success and improvement, and broadening of the JetBrains products pretty much demolishes the argument that Java has declined and fallen on the desktop. JetBrains is an existence proof that it is a very capable platform for anyone who chooses to use it there.