This is a gross misunderstanding of a rich domain model. A domain model should depend on nothing externally, except via interfaces which are a part of the domai

This is a gross misunderstanding of a rich domain model. A domain model should depend on nothing externally, except via interfaces which are a part of the domain model. The real tl;dr is that if you can't run and test your domain model without a database, UI, external services etc, it likely is not a domain model in the first place. Your misunderstanding is common when ignoring the provenance of the pattern: the place for it is "when you have complex and ever-changing business rules" (page 116 of Patterns of Enterprise Architecture). If "user.render(engine)" or "engine.render(user)" are operations in your domain model (and are, as I assume from your post, UI related operations) the domain model is being used as an architectural pattern rather than a business logic organization pattern, in which case none of the stated benefits hold because of misuse.