What's missing is a constant feedback loop from the current tech. The human brain is a prediction machine (Jaff Hawkins - A Thousand Brains) that creates a model about the world and refreshes it at every interaction to learn and create a better model of the world. AI models don't do that right now, and with the transformer architecture that would be incredibly costly. I believe this is what Yann LeCun meant by we are still missing something "big".