If Rey's parents were always supposed to be someone important, nothing in TLJ keeps that from happening. JJ Abrams hadn't even finished editing TFA when Rian Johnson started writing the TLJ script (and the two of them were having conversations about what TFA was setting up). Nothing was undone by TLJ.
People treat it as though Kylo wouldn't lie to Rey . . . in a movie where he already lied to her about Luke trying to kill him (and clashing lightsabers with him).
Kylo lies. To paraphrase Margot Robbie's Harley Quinn: he's a bad guy . . . that's what they do. At the very least, whatever he did actually see could be nothing more than a mere part of her story - not the entire truth.
Rey was dropped off on Jaaku and handed over to an abusive junk boss (who chased her across the galaxy and threatened her before Chewbacca ripped his arms out in JJ's own deleted TFA scene). So all along, whoever dropped her off didn't worry too much about leaving her safe with someone trustworthy. That was established in TFA, not TLJ!
It makes more sense that,
all along, she was sold by "filthy junk traders" to a junk boss who'd turn her into a scavenger. But that doesn't mean that those filthy junk traders were her natural parents. The idea that caring/good parents would leave her with Unkar Plutt is ridiculous. Fans need to realize that some things just shouldn't be revealed until the final act. If her original parents were always meant to be someone important, everything is still in place for that reveal. Nothing has changed. Whether Rey's true parents were "nobodies" or "somebodies" is up to JJ. And it always was.