I assume that "Talk to your data" presupposes the existence of some simple view that has been created and that embeds 99% of the required business logic.

"What was the average order size per customer for product XYZ in the West region?"

Imagine turning that one loose against the typical legacy system.

I wouldn't trust an LLM to figure out the joins or aggregate calculation, LET ALONE the definition of a customer, a product, or a region.

But it would almost certainly generate AN answer.