Agreed on DM making the experience special. The cognitive load on a DM is very high though. They have to digest information on the game setting and the monsters, synthesize scenes and react to players' interactions all the while staying true to the narrative. I think LLM's can play a big part in assisting human DMs by either providing low-fidelity ideas for "inspiraton", commonsense based on their training on D&D texts and literature or high fidelity text in some cases to be directly presented to the players.