Hm, the reactive manifesto doesn't say that it's new. It tries to convert people from bloated ol' Java/CSharp to better practices that fits new common needs. Of course Reactive is not new... Nor realtime... But an ecommerce website for instance never had to wonder about this kind of things before: new needs.

It is not just about Java bloatware, it is already obvious that it is crap and several "fixes", notably Scala and Clojure, are already matured. It is mostly about understanding and avoiding other broken by design things, such as thread-mutex based "concurrency", mutable, non-parallel collections, and imperative programming (all these Java loops which do mutations) in general. It is about ideas summarized by Joe Armstrong in his thesis, that the world is parallel and that actor model and share nothing architecture together with fault tolerance and message passing via unreliable channels as the only way of communication coul is a more appropriate paradigm than current imperative-pthread-mutex mess.