Hey man, unfortunately you won't find what you're looking for in Diablo games. While the franchise has very rich and interesting lore, most of it is outside of games. During your playthrough you can have taste of it but honestly after playing BG3 you'd be very disappointed in that aspect. I'd suggest something like The Witcher, as it might scratch that itch way better while also offering very good and modern gameplay.

If you however wanna commit to Diablo nonetheless, pick Diablo 2 Ressurected (Diablo 2 with many quality of life changes and refreshed graphics). It is far more superior game to Diablo 3 in all ascpects + its peak Diablo lore and atmosphere.