Review a code change for structural regressions that make code harder to change, delete, or reason about, including complexity moved rather than removed, missed simplifications, shared-path special cases, oversized files, wrong-layer logic, thin wrappers, premature abstraction, dead code, coupling, vague names, data-locality smells, stale comments, and type-safety holes. Use when reviewing for maintainability, simplicity, code structure, or design quality.