CRDTs may solve most of the technical side (albeit with lots of complexity), but how do you solve the “how to explain what happened to the user?” issue? Not all actions are intuitive while offline.

For example, if 2 users are both offline and both buy the same last item in the retailer’s inventory. The race condition has to be solved sometime, and the non-winning user will need a communication from customer service apologizing for overselling the item. Those are pretty frustrating conversations when they come from airlines or hotels.