Also: making Vader Luke’s father helped Luke’s character just as much as Vader’s. Vader was given a whole new layer of depth (being more then just cold-hearted monstrous bad guy, also being turned into a man who has fallen, who was once good but became a monster) while Luke was forced to face the fact that his father wasn’t who he thought he was, overcome his hatred for him and instead choose to love him, choose to confront his inner demons and fear that he’ll become just like his father, and also be a Jedi independently of his father. Originally Luke only wanted to become a Jedi because his father became a Jedi. But Luke finding out Vader is his father makes him become a Jedi for himself and not because he wants to live up to an idealized version of his father. Because him realizing Vader is his father crushed him, because it shattered his illusion that in order to become great he needed to be just like his father. But he’s a Jedi not because of his blood, but because of who he is. Luke thinks he’s destined to become what his father was, and when he found out his father became evil, he fears he will too. But Luke grows beyond this and becomes his own man rather then just trying to live up to his father, and in the process, redeems his father.
The irony of you saying Vader being Luke’s father makes things too connected by family is that Luke’s arc after realizing Vader is his father is about him choosing to be his own man and not just follow in the footsteps of his father. That he’s more then just his blood. He becomes a Jedi despite his blood, not because of it. Just having him want to be a Jedi just because of his father is shallow.