Better questions to ask: Is it good work? Will you find it fulfilling? Will they treat you well or will they treat you like a cost center? Sure, 80% of places don't use whatever newfangled tech you care to name, but that's not the whole picture.
80% of places are probably places you don't want to work, so what good is it to say "80% of places "? You don't care about the majority of places, you care about the ones you would actually want to work at. What do people in those places do?
The point I'm driving at is not exactly that you should learn new stuff to work in a good place. Rather, the more options you have, the better chance you have at getting into a line of work you actually want to be in. And sure, it is possible that you will end up using Java in that line of work.
There are reasons people use newer tech. And not all of those reasons have to do with being addled by ADHD and obsessed with shiny things. I get tired of that implication.
Remember that Java 8 (or whatever tech you care to name) was once upon a time the new shiny stuff.