Are you suggesting that a polo shirt will cut it on formal night? A polo shirt would never be considered formal wear but can be dressed up if it’s a fine quality (Zegna, Bruno Cuccinelli, Façonnable, etc…) paired with a jacket. The run-of-the-mill cheap Ralph Lauren would not. But stylish does not mean formal.
And only in Hawaii or a small South Pacific island would an Hawaiian shirt by considered dressy.