AutoMapper

Developers manually rewrite object properties line-by-line instead of using established mapping libraries like AutoMapper. This is tedious, error-prone (easy to omit properties), and leads to maintenance difficulties with complex object models.

AutoMapper has become the de facto mapping library in .NET despite its own creator recommending against use cases where >80% of fields are manually mapped. Developers adopt it even when inappropriate, leading to unmapped field issues and invalid mapping flags.