I think they're adamant about this due to problems with time passage and turn-based/multiplayer, but... I would so, so love this. Day/night cycles and weather have such a huge impact on a game's atmosphere. It was true even in older games like BG1/2 and Morrowind, but modern(ish) games just showed how amazing these elements can be. All those Witcher sunsets and Skyrim's bleak (or sunny!) weather. Makes the world much more believable, alive and immersive. There's so much lost potential here with BG3's impressive graphics. (Fog of war would diminish it a bit, though.)
And it's impactful in terms of gameplay, too. Wait until nightfall to infiltrate a camp of diurnal creatures or creep through a city unnoticed. Wait for daytime to explore a graveyard with a low-level party. One place can be wildly different during the day and during the night. Breath of the Wild had a great weather system, though of course it's a very different type of game.