Discussing levels of complexity quickly gets pretty subjective. It is possible that Rama has found good abstractions that hide a lot of the complexity. It is also possible that taking on more complexity in this area saves you from other sorts of complexity you may encounter elsewhere in your application.

However, there is just more going on in an event sourcing model. Instead of saving data to a location and retrieving it from that location you save data to one location, read it from another location, and you need to implement some sort of linker between the two (or more).

This also comes down to my personal subjective experience. I actually really like event sourcing but I have worked on teams with these systems and I have found that the majority of people find them much harder to reason about than traditional databases.