It's not an attack to question the efficacy or significance of an elected official's actions. AOC publicly identifies with the socialist project. Not only that, but she and Bernie Sanders are the de facto standard bearers of said project in the public eye.

As a socialist who has been committed to this cause my whole life, I evaluate politicians based on whether their actions move the needle forward.

AOC attending the Met Gala is an action that takes place in a larger context of her veering further away from the movement that put her into office and closer to the political establishment.