I am an unrepentant ROTJ apologist and I fancy myself the blue elephant in the room, as you can see from my name.
I see nothing wrong with the idea that Force sensitivity can run in families. That doesn’t mean anyone born into a family will have it nor that anybody else can’t.
Leia could well have been suppressing that part of her psyche because it was at odds with her upbringing or simply uncomfortable for her to admit. Don’t forget that Leia was the one to sense Luke hanging out under Cloud City in ESB. You could say that was all Luke’s doing or recognize it was the first inklings that Leia had latent sensitivity to the Force.
In ROTJ, when Vader referenced the possibility of using turning Leia to the dark side, that was clearly a threatening tactic, not total confidence that Leia would be powerful simply by virtue of her relation.
The idea that anybody could harness the Force if only they tried is far less compelling to me.
Firstly, let me just state that I have no desire to trash your love of ROTJ! My comments are meant in playful fun (just to be clear since internet tone can be misread as easily as Jedi prophecy!).
I’m not so much bothered by genetic Force potential as I am the extent to which the saga eventually leaned on it. The idea of Luke inheriting his Dad’s talents is fine - indeed I think it’s a big part of the SW mythos. He was a ‘great pilot’ like his father, he had much anger in him “like his father” etc. I think the Leia thing just pushed it a little too far, mainly because it was thrown in there purely to tie things up and answer the question of the ‘other hope’. The prequels then kicked the whole thing off the cliff with midichlorians and Chosen Ones and the Force conspiring to balance itself. I just prefer the more Zen version of the Force and the subtler implications of lineage/heritage presented by ANH and TESB.
The point I was making is that Rey’s powers seem to reflect that later SW idea - that she is/was somehow ‘chosen’ or special or loaded with midichlorians via a particular lineage - hence all the speculation prior to TLJ. The revelation that she’s just a regular joe (a revelation I really liked in theory) seems incongruous with her ease in mastering the Force.