You are absolutely correct, OP. And in my view, Larian deliberately left Tav underdeveloped as a way to pressure players to use one of their pre-gen origins, which is what they want us to play as. It is a cunning way to force us to play as one of their origins, and that is complete b.s. Like you, I also will never ever play one of their ridiculous origin characters but still fully expect that I should be provided with a player character that I create that is fully tapped into the game. This is not something too much to ask for. Games like DA, PoE, even the Pathfinder games, and most notably BG2, all do this far, far, far better than Tav in BG3. So, it can be done. It has been done by others for years. But Larian deliberately chose not to do it in BG3.
As a side note, I hate the concept of their origin characters so much that I would want to just slaughter each and every one of them because I see them as the characters that don't belong in my game. But Larian has made sure we can't do that either, by tying huge chunks of the game's story to those origin characters such that removing them from the game would effectively remove huge parts of the game's story, quests, and content.
