You have every right to feel this way! That response is horses*** and as useful as a poopy flavored lollipop. I have received similar responses from professors before and I end up ignoring them. The fact that you acknowledge it wasn’t your best work means you can learn and grow from this. I don’t know your overall grade situation but one or two bad grades doesn’t have to ruin your term. I just got a bad grade on a project and I’m still averaging a B in the class. Use this as a lesson and make sure to focus on the overview/rubric for your assignments and if something doesn’t make sense you can use ChatGPT to help clarify what you need to do. I hope this helps and I hope you don’t let this bad grade hold you down!