I don’t know about Java, but we’re seeing a shift to functional in the mobile space, where non functional code is definitely “old” code. In Swift with Combine and in Kotlin with their thing.
If you take the time to look into it, you'll discover that the functional style is only a change in the "fashion sense" to those who are totally oblivious to their advantages.
I get how the pedantic take on monads turns people away from the functional side of programming, but you'd be hard pressed to find anything to criticize how returning either/result monads from promises is not a huge improvement over the boilerplate-rich/pure OO approach to Java.