The reason the bloodline thing is stupid is because it's taken to mean literally.
When Yoda and Obiwan and whoever discuss Luke and how he's like his father, they mean in terms that he is implied to have the same vulnerabilities as his father. In the OT, we don't know Vader's past, so all we know is that he was once a good Jedi and then fell because he was seduced by the dark side. Now, this is actually a plotpoint I have similar criticisms that I have with Rey, because I don't feel Luke has any attraction to the dark side. All that really happens is that Luke gets a bit too angry and wants to kill Vader when he threatens his sister. That's it, it's a very human instinct and very relatable, but I don't think it's something that makes a lot of sense as leading to the dark side when Luke has canonically killed plenty of far less evil people in combat. Yeah, at that point, vader was defeated and helpless, and you probably shouldn't kill people lying on the ground, but it's still fairly small potatoes with regards to who Vader was.
But the point is, if Vader can fall to the dark side, anyone can, and certainly his son who has a tendency to act before he thinks. That's all the 'bloodline' amounted to and it's why Leia never really struggled, since she's a cooler, more even-keeled sort of person. It's not that Luke had the genetic code for darksidedness, it's that he was rash and angry, like his father was.
Whatever the shortcomings of trying to convince Luke is susceptible to the dark side are enhanced a hundred fold with Rey. Unlike Luke, she has no history with Palpatine. Unlike Luke, she has never really had "Too wrathful in seeking vengeance" as a character trait. With Rey, the only thing she had as a vulnerability to the dark side was her loneliness and desire to find a place in the world, which Kylo Ren tried to put pressure on to join him. But with Palpatine, he's like "Here Rey, be completely fucking evil so I can possess your body and rule through you as you helplessly watch from the inside as I do horrible shit."
Like...there is nothing of Palpatine in Rey and to introduce that as a conflict is an absurd decision. It's only credible if you sincerely believe that there is a gene for evil that Rey somehow inherited and is therefore succeptible to it, even when everything about her character is opposed to it.
And it's just as fucking bullshit as it was with Daenerys Targaryen.