Well I don't think functional languages are something new and by reading the latest death and doom I'd wonder how we ever got this far and why suddenly it's so much harder to do concurrency. I confess that I don't write low level software for lunar modules but just the regular enterprise stuff and having worked with high level concurrent constructs like ConcurrentHashMap, LinkedBlockingQueue, RingBuffers on the jvm I've yet to experience the concurrency issues everyone is lamenting. I know it must be hard for the people developing the jvm to make those high level concurrency constructs available for me, but that is why I'm grateful for their work and "happy" that I can rely on them. I don't know maybe I've just been very lucky until now.

Most of the bugs I see in the wild are of the "runaway state" variety; in other words, a state the programmer(s) involved forgot to imagine might happen. This class of bugs includes EVERY bug or crash that is fixed by a restart of an app or system (because all that does is reset state to a "known" a.k.a. "modeled" state, bringing it back within the code's, i.e. programmer's understanding). Therefore, anything (whether it is a language, a methodology, or both) which mitigates or eliminates this class of bugs would be HUGELY valuable.

Functional paradigms/languages, and immutable values, and controlling side effects, greatly help with that, in my front-line coding experience. Therefore, I am a fan.

Do you enjoy doing needless extra work? In other words, are you a little bit lazy? (in the Larry Wall "laziness/impatience/hubris" sense). If so, you should be at least trying out functional paradigms and see if they work for you like they have for pretty much everyone else who has taken them on.

I'm going more pragmatic and I think most of the bugs were/ are NullPointerException the kind that today's IDE(due to their maturity of working for years and years with the language) can now even warn you about, compared to obscure ones that force you to do resets. On the other hand I don't see why the concepts of immutable values cannot be adopted in OOP languages. There is http://javaslang.com/ and immutable collections were long time present in Guava library. Sure immutability might not be enforceable in the language itself but you can do it. Java8 has streams for a functional approach to collections. Hell you can even use Akka if you cannot do without an actor framework in java.

But suggesting we need to start from scratch with new untested 3rd party libraries(that other people take for granted) and rewriting some of them. Even the simpler stuff like suffering the quirks of the extra tooling(build tools, IDEs) for a new language and all because of the death and doom we are supposedly seeing today(which I dont and I've yet to see people doing nightly restarts of web servers for some years). Unless you do consultancy for that language(or are seeking employment in a niche market) I think it's a little mad.

For me to declare the defeat of OOP and win of a FP language I first need to hear the voice of people having to do maintenance work on legacy code in that language as I'm too old to only believe there is such a thing as panaceea or there are only upsides to an alternative.