If the lore, characters, story, and side-quests don't do anything for you, I think it's just not for you. I wonder though, what are some Western Role-Playing games that you think have done things better than The Witcher 3 here? I can name a few, but not many.
If you're comparing it to behemoths like LoTR and GoT I can see why it is disappointing for you.
Personally, for me the interesting thing about the game is how the side-quests of each area are interrelated and reinforce a general story. It all came together when I found how two particular side-quest lines were related in Velen. The game and its inhabitants are suppose to be depressing.