The phrase "gotten the idea" implies that you have understood something or come up with a plan. However, there are several antonyms that can be used to describe the opposite of this phrase. For example, "confused" might indicate that you don't understand something, while "ignorant" suggests that you lack knowledge. "Misunderstood" implies that you have grasped something incorrectly, while "uninspired" suggests that you haven't come up with any ideas at all. "Stymied" suggests that you've been prevented from thinking or acting, while "distracted" implies that your attention is focused elsewhere. By using these antonyms, you can express the opposite of "gotten the idea" in a variety of different ways.