If you recall, the second trailer to TFA starts off with the classic quote from ROTJ: "The Force is strong in my family. I have it. My sister has it." And its topped off with "You have that power too." TFA was mainly about Rey's journey to the awakening of the Force in her and a lot of people were hoping those words would explain her connection to it, why Luke's saber called to her, why she heard the voices of Jedis who she didn't know and who passed away before her, and how she could adapt to her powers so quickly.
Ah, I actually didn't watch any of the trailers. I skip trailers for most Star Wars movies nowadays, because I don't want my expectations to be built up in one direction or the other. I'd rather just go in a blank slate and take the film as it comes. So far, I think the only one I've seen is the Solo one.
That's not a dig against you, either, by the way. I came by this attitude after the TPM trailer, which looked AWESOME and was....well....TPM. :-\ After that, I stopped riding the hype train for Star Wars movies and basically would do media blackouts for films. Again, Solo is the only exception to that so far, because I'm investing almost nothing into it emotionally. I'm merely curious as to whether it'll be any good.
Anyway, to your points here, the basic issue sounds like "I thought there was gonna be a reason why she has this ability, and now there isn't." Please let me know if that doesn't really describe it, though.
If it does, however, I think that the films show that to some degree, just perhaps not in a way that you care for. It's not (as I recall) ever explicitly stated, but Rey has these abilities because the Force chose her. I can hazard guesses as to why, based on what we see in the films, but the answer as to why the Force picked her, I think, is
because she's a nobody. Kylo Ren/Ben was a "somebody" and clearly, his power in the Force has run amok, destroyed the Jedi order, led to him killing his own father, try to kill his own mother, try to kill his uncle, etc. In short, Ben has ultimately failed the Force or at least needs to be countered.
I think the ultimate message of the film is that the Force is not a matter of bloodline or destiny, and that instead, there is an aspect of the Force that is manifesting in not merely Rey, but also the "nobody" who is the stable boy on Canto Bight. It would seem the Force is "choosing" nobodies now, perhaps because "somebodies" have proven to be unreliable custodians of it. Or maybe the Force is manifesting in the
best of people -- the ones with the most reason to give in to anger, hatred, and despair, but who instead have chosen to help those in need the way Rey did with BB-8, and the way the stable hand does with Rose and Finn. Maybe that's the only way to balance out the evil that Ben has allowed himself to be consumed by (and maybe also the Knights of Ren?).
Anyway, let me flip this around. Suppose it's revealed in Ep. IX that, in fact, Snoke was lying all along, and Rey was actually the child of Obi-Wan's secret daughter (with Satine Kryze?). So, Rey's a Kenobi by bloodline. Would that make things all that much better? We say she's a Kenobi and boom, everything falls into place? For me, at least, that's just as much a cop out as saying "She's able to do all this stuff because the Force chose her." The Force chosing people makes just as much sense, and ultimately (to me) sends a more hopeful message: you don't have to be born into it; anybody could use the Force. Even a nobody.
