A combination of systems driven gameplay and narrative, where you character build gives you tremendous room for creativity and self-expression with how you choose to tack challenges, overcome obstacles or just move around the map.
Think about the approach to Aunt Ethel’s cavern. There is a multi-tiered descent covered with poison gas. How many different ways are there to bypass that? How many different spells or abilities can get you past it? It’s a simple puzzle that illustrates the strength of Larian’s system driven approach.
BioWare and Obsidian never gave players that much freedom in gameplay. Bethesda did, but at a significant cost to narrative and presentation. Their world’s are reactive but only in a shallow way.
You don’t think BG3 is innovative? I’ve never played a game quite like this before. DOS2 is obviously very similar, but this is pushing the idea much further (a bigger budget tends to do that).