I think Mean Girls is a masterpiece of the New Sincerity Movement (Post-post modern). The way it uses irony to burn down flawed, Hughesque, perceptions of teenage existence and high school, and then builds a sincere vision at the end fulfills the thesis in an inspired way.

Not to mention it's a comedy where nearly every joke elicits a laugh, and where setups service multiple punchlines, and punchlines serve as setups for future jokes.

and typically film lags behind literary movements, so I think Mean Girls is also quite ahead of its time which is why i's still so enjoyable to watch today