I think it's a question of internalization. When you have internalized the correct way to think about it, it feels obvious. And wrong ways to think about it seem absurd. We stand on the shoulders of giants, Plato being one of them. We have internalized their philosophy. And that's why it feels idiotic.
But understanding what their point actually was and what other conceptions are/were possible is also a huge insight. In this parable: jumping from the shoulders next to them, to see how actually large they are.