Rx is neither simple nor easy, for non-trivial projects. Its an incredibly leaky abstraction and you end up having to understand the internals to do non-trivial things. Understanding when something runs in what thread (and in RxJava knowing when to use subscribe/subscribeOn/observeOn was much harder than it claimed to be), how to correctly handle errors, retry failed operations, apply backpressure without dropping data — these things essentially force you (in my experience, at least, but I’m no Rx expert, just used it for a few months) to dig into the internals to understand how they work: ie not simple.

But because of its lack of simplicity, it was also incredibly hard to use, to make it do what you want. So it was neither simple nor was it easy.

(And yes, I buy into the differences between simple and easy)