This is the old debate whether applications should be tightly or loosely coupled. As the article concludes, there are tradeoffs to consider - the broker is a SPOF indeed, but on the other hand it'll take care of all the queueing logic (which is not that simple as it seems - acknowledgements, backpressure, redelivery, timeouts etc etc). It's also much easier to scale the system out if applications are loosely coupled.

Furthermore, a good broker supports some kind of failover. We run a RabbitMQ cluster behind a load balancer, and it works great - once e.g. we had a hardware failure, and the applications did not notice anything from it. Of course we also have to monitor the queues on the broker (one of the few ways to bring down Rabbit is to fill up its disk). But having a central broker for connecting apps also means you have a central point you can keep an eye on to check where your bottlenecks are (which queues build up).

Loosely coupled applications are also much more unix-like in the sense that you can make them do one thing instead of baking in your custom restart logic (over a network? please don't).