In many engineering applications, numerical models are validated by comparing their modal properties with those obtained from an experimental model. Among the existing correlation tools, the Modal Assurance Criterion (MAC) is one of the most widely used indicators to compare mode shapes. However, when dealing with closely spaced or repeated modes, the MAC may provide misleadingly low correlation values, even when the numerical and experimental models are physically consistent. This work addresses the limitations of the classical MAC in the presence of closely spaced or repeated modes. Discrepancies between models are often not related to modelling errors but to a rotation of the mode shapes within the modal subspace. To address this issue, this work applies the Rotated Modal Assurance Criterion (ROTMAC), an extension of the MAC that accounts for rotations of mode shapes within the modal subspace. The proposed approach is illustrated through numerical examples involving structures with closely spaced and repeated modes and is further validated using experimental data. The results demonstrate that ROTMAC provides a more robust and physically meaningful assessment of model correlation than the classical MAC in scenarios where modal subspace rotations are present.