I am in the exact same position as you. Like you, I started D2 in 2020 and only played once or twice and started the original quest line then. Decided to come back almost 3 years later and trying to get more into but just cannot get past this Learning Light bugged quest and I sure as hell do not want to make a new character after grinding several hours to get guardian rank 3 (almost 4). I'm literally just trying to unlock Iron Banner too and I can't even do that.. So infuriating.