I have studied Java GUI programming for a while. I found Java Swing frustrating, because it causes some problem when using some high resolution screen. (For example, surface) I studied Java FX, and I thought it easy to use and my code is cleaner than Swing. However, it seems that Java FX is not popular at all. Or nobody uses Java to make GUI work today?
I think java is used a lot in the backend. As you said, java fx is not that popular. And now in java 11 java Fx is exported to openjdk and it is no longer part of the jdk. If java FX were popular than no exclusion from the jdk should happen.