If your image of BG2 is a light hearted fantasy filled with silly humor, we definitely did not play the same game. For a game that came 15 years before Witcher 3 and GoT, I would say it is very dark. The Spellhold sequence that many people are criticizing is specially dark and masterfully delivered as I posted in the video last page.
Yet, 20 years later im BG3 we have an evil vampire spawn making jokes every sentence about blood drops, while he has an impeding fatal doom.