The entire field of Mechanistic Interpretability exists because just understanding Attention does not in any way help you to understand why a certain NN responds with a certain hallucination about a certain Chinese boat in this specific context.
> The only remaining thing to study is the data and weights
To me this is like saying “the only thing left to study in the brain is the connectome; probably going to be boring, we understand it already”. It’s almost all of the hard/meaningful stuff! It’s where intelligence and consciousness lives!