Are all languages really equally good? Is C really no more productive than assembly? Is Swift really no more productive than Objective-C? For many higher level applications is Java really no more productive than C? Doesn't using something higher level like Python make certain kinds of tasks easier than the same task in Java?
Since the inception of programming languages, there has been continuous improvement of the existing languages as well creation of new languages, both of which have introduced new paradigms and features to programming. These new features and paradigms often replace older features and paradigms. Not everything works, but much of the time the new features and paradigms have made writing and maintaining good programs much easier.
Unless you believe our current tools are already completely optimal, it seems only natural to try to improve upon them.
So is your argument that programming languages in a generation will be equal productive/un-productive as what we have now? That seems too pessimistic to me. I think our tools will be much better, just as I feel our tools now are better than they were in 2000 or 1990.
If the argument is that functional programming is not an improvement, that's fine, how do you see languages improving? What's the direction they should take?