> The problem when using REST "correctly" is that the way your objects interrelate is not necessarily the same way on the backend as it is on the UI. So you end up creating custom REST endpoints for complicated UI that does not map directly to how your objects are related in the database.

Not defending the article here, but I don't see this as a problem at all. Yes, you API objects should not necessarily map directly to your persistence layer; that is a good thing. The problem domains of the UI and the persistence layer are completely different and should therefore be modelled differently. Your API mediates between the two, acting like a repository for your UI models and abstracting away the persistence layer completely.