Lecun's argument is based off a bad interpretation of how data is processed by the optic nerve, we don't receive that much raw data.

What we do have, is billions of years of evolution that has given a lot of innate knowledge which means we are radically more capable than LLMs despite having little data.

There is more to text than just predicting tokens based on a vast volume of text.

There isn't an argument "against LLMs" as such; the argumentation is more oriented against the hype and incessant promotion of AI.