Episode 8 was where Rian Johnson got the opportunity to put it in. Unfortunately Disney had no overarching plan and continuity for the trilogy. While I have my complaints about TLJ, it at least had arcs for the characters, and built in an interesting direction on TFA's tease of Rey coming from nowhere. Johnson went with the idea that it's NOT all about special bloodlines- that power and virtue can spring from "nothing". That any person can have the potential to be heroic, to be a Jedi.
Then RoS went back to "everything is about the magic families". Yuck. In addition to wasting/betraying Vader's whole arc by bringing Palpatine back.
I'll certainly agree that Lucas had his issues too.