Star Wars doesn’t (or didn’t, at least) have an obsession with bloodlines. It doesn’t (or didn’t) have some “divine right of kings” thing going for it.
The central Saga films (before the “Skywalker Saga” title, which I believe was used sporadically well before TROS’s production) just featured a generational family story, about a single family, and one that had extremely humble origins among slaves, with a creative and even subversive take on the Chosen One storyline - the fact that Anakin is expected to be a Messianic figure but becomes more analogous to the Anti-Christ is the biggest reason why, dramatically speaking, that element of lore-work was still unconventional and creative.
And honestly, I’m always a bit confused by people thinking that explaining how Luke and Rey are separated *has* to be some kind of liability - the lost prince or princess trope is all over the place in legends and media, as are different and dramatic ways to portray its fallout. Indeed, the idea of Rey having to tackle her abandonment issues with whatever mysterious story Luke would have about it was part of the attraction of he story... as would the idea of perhaps reversing Vader&Luke’s chemistry, where instead of two enemies discovering a familiar bond and it eventually bringing them together, have Luke&Rey discover a familial bond that actually drives them apart when they can least afford that.
I WILL argue that there can be and *is* actually a way to do the “family in spite fo blood” story, or to sell Rey as a Random... but you can’t do that while simulataneously trying to treat Kylo/Ben as special because of his lineage and inevitably going through a redemption because he can’t deny his blood ties... but that also requires ending the family story of the Skywalkers on a diner note that no one really wants.
Rey’s bonds to Finn and Han, and her overall story in TFA, is plenty strong, and doesn’t necessarily succumb to any issues when faced with Kylo, because he’s by and large a deconstruction of the Skywalker archetype - a selfish, self-centered, and entitled brat with no redeeming qualities and more loathsome than intimidating. But again, you have to admit that him as the only Skywalker is a needlessly spiteful revocation of the happy ending from ROTJ.
TLJ shows where things got screwed up. You can’t treat Kylo as special, pretend that his past as Ben matters more than anything he does to Rey, the Galaxy, or her friends, and then try to pretend that an underdeveloped and tepid version of Rey you’re writing is strong because you waste her time on an anti-climactic mystery where she’s revealed to have no connection to the family story that Kylo is basking in... and then exile her from the final confrontation.
To me, there were two decisions made by TLJ that kind of just doomed certain objectives that LFL later discovered they wanted when making Episode IX:
-LFL decided they wanted a Rey on par with Anakin or Luke, a satisfactory ending to the Skywalker family story, and Ben Solo redeemed.
But...
- You can’t do all that when the only Skywalker left is a shallow, patricidal Neo-Nazi with no redeeming or sympathetic qualities, that only Skywalker is Ben Solo, and Rey is in danger of being overshadowed and overwhelmed by Ben because of his lineage and crapping writing of her around him post-TFA.
Really, the only big way they could have done this would be to either a) retcon Rey into a Skywalker, and thus dump TLJ, or b) retcon Ben and reveal he wasn’t really a Solo, and thus undermine the entire reason poeple had for arguing he “had” to be redeemed.