It's not true. I checked http://zguide.zeromq.org/page:all and it would only take 332 pages to print it all out. And to understand ZeroMQ you only need to read the first few pages and skim the rest. That is enough to see that ZeroMQ is a serious attempt at letting you use the same design patterns that you would use with Message Queuing over top of plain sockets, i.e. there is zero Message Queue system behind the curtain. 0MQ is useful because these design patterns make it easier to build correct and powerful applications that leverage network connectivity.

I have built applications that use both AMQP messaging with RabbitMQ and ZeroMQ for the parts where an MQ broker was not necessary or where it would impact performance.

The arguments swirling around ZeroMQ and sockets are the same ones that swirl around threading and higher abstractions. We now know that it is hard to write correct programs using threading unless you refrain from using locks and either have all state immutable or you use lock-free access techniques. There are many libraries (even for Android and iOS) that encapsulate threading with a task-oriented layer that communicates between tasks/threads using queues.

Sometimes you have to make a decision NOT to do something that you CAN do, because of the greater good of the work.

It's no different than any significant technology that has few antecedents. Once you know the background and cast away assumptions and fallacies, it's much easier of course.

Read the ZeroMQ guide for yourself. It is IMHO one of the finest (and funniest) ever written.

It is not true, at all.