Yeah, if you can get away with that model things are simpler. The best first step into SOA to take is offloading work that doesn't need a user response to a pool of workers (often by publishing to a message bus, as mentioned elsewhere in the thread). I've implemented systems like that using Rabbit and Redis and it worked fairly well.

However, some kinds of requests are fundamentally about integrating the results of a bunch of different services into a response to send to the user. In that case you somehow need to gather the results of your rpcs/events in one place to integrate them. An example is Google search where the normal results, ads, and various specialized results/knowledge graph data need to be integrated to present to the user.

Another consideration is how much you want to be able to isolate services. If you have a user/auth service as in the article which completely encapsulates the database and other resources needed for data about users then you'll end up with a lot of calls into that service. It's a disadvantage because of all the reasons in my original comment, but it's great from the perspective of being able to isolate failures and build resilient systems