From D2 to D3 they completely tore out the Christian mythology and association with the existing legends. Things became kid-friendly. Pentagrams were changed to

From D2 to D3 they completely tore out the Christian mythology and association with the existing legends. Things became kid-friendly. Pentagrams were changed to imprecise scribbles in circles. Angels became "angels" in name only, with a completely new origin story. They removed any concept that anybody was acting contrary to the Christian God, and just made one of the angels the king of the universe. I'm won't go into the Tyrael fiasco. Basically, expansion of made-up lore and a loss of mystique about connections to the real world ruined the sense of being in an unwieldy no-hope situation. The story instead felt like it was written by a teenager with a power fantasy.