I sent an email with the picture to 1K Voice, here is the response:
I'm sorry to hear that you were disappointed with the meal you received on your recent flight. It does not look very impressive to me either.
Our chefs are committed to providing exceptional meals, and I have shared your honest feedback with our Catering Operations team.
We appreciate you choosing United, and hope you'll give us the opportunity to provide you with a more positive experience in the future.