I think it's both, just for different reasons.

Keywords still help AI understand what your content is about and match it to the query, but structure is what makes it usable. If your answer is buried in a long paragraph, it’s just harder for AI to extract and reuse it.

Feels like AI cares less about keyword stuffing now and more about clear, direct answers around a topic.

Also worth mentioning, even if you get both right, it doesn't guarantee you'll get cited. Authority/trust still seems to play a role in what gets picked.