I certainly wouldn't dispute that it can be hard to reason about concurrent operations in traditional database systems - particularly if you want to do it acros

I certainly wouldn't dispute that it can be hard to reason about concurrent operations in traditional database systems - particularly if you want to do it across multiple database systems, which do indeed have differing implementations. That said, if the author thinks eventual consistency is easy/not-that-bad/whatever by comparison, I would tend to question their understanding of programming for eventually consistency. Eventual consistency for non-trivial applications is really, really, really hard to get right. Consistency in relational databases is a hard topic because maintaining consistency in any concurrent system is hard. Traditional systems provide you with a set of tools (isolation levels, foreign keys) that make a decent programmer capable of building a safe concurrent application. Throwing away those tools and replacing them with nothing does not make life easier. The tool is easier to understand, but the problem is harder to solve.