The original Relational Model of Data for Large Shared Data Banks [acm.org] was a major milestone in the history of information technology that has undergone changes in understanding over the years. Despite Design Constraints and Unavoidable Realities [kimballgroup.com], A Review of Relational Concepts [wikipedia.org] is useful to avoid widespread Logical-Physical Confusion [information-management.com].
That is not to say that the real world always maps well to the simplest logical structures, after all Starbucks Does Not Use Two-Phase Commit [eaipatterns.com]. Also, aside from logical correctness, the problem of Basic Human Error Rates [hawaii.edu] must be also managed into any data quality metric.