Why do I pretend to accept feedback and then ignore it?

You have learned to look receptive without being receptive. You nod, you say you will think about it, and then you quietly set it aside. Naming that honestly, as you just did, is more than most people manage, because the performance is comfortable and admitting to it is not. It is worth asking what the nodding protects. Often it is a way to end an uncomfortable moment quickly, or to avoid the harder work of actually sitting with a criticism that might be true. The trouble is that the feedback you dismiss is exactly where your growth was hiding, and performing openness slowly costs you the trust of people who can tell the difference. Try this with the next piece of feedback: do not respond in the moment at all. Just write it down, exactly as given, and come back to it a day later when the sting has faded. Ask honestly whether any part of it is true. You do not have to accept all of it. But actually weighing one piece, instead of performing that you will, is how the real skill of listening starts to grow.