I just stumbled across this article from January, and I've got to agree that most of these theories are truly bonkers. Let me count the ways.
Looking at theories 4 and 12, it seems that some people don't know how to calculate the passage of time, since these proposed parental events would have happened too far in the past for Rey to be only 19. I also wonder why so much speculation revolves around her parents having Force abilities. Nothing in the Star Wars canon that I'm aware of dictates that Force users must be descended from Force users. And the idea that the Force can somehow engender virgin births is one part of the prequels that I can happily ignore. Perhaps some Force-user impregnated Anakin's mother and then used a Jedi (or Sith) mind-trick to make her forget about the experience.
Popular Theory #1 seems the most likely explanation. Personally I don't want Rey to be related to the Skywalker dynasty at all, because I'm sick of the whole Star Wars universe revolving around them. But if she is related to Luke, they'd better come up with a really good explanation of why she was left on Jakku with no one to look after her. It could be a David Copperfield sort of story, or Oliver Twist, in which she did have a guardian but something happened to that person and no one was aware of it or able to do anything about it. Maybe Luke couldn't go fetch her because he was busy fleeing from someone, or trying to save Ben Solo, or fighting with the Dark Side somehow. Perhaps he could have been marooned on Ahch-To. Just because he's got Force powers doesn't mean he can whip up a spaceship or fly unprotected through the vacuum of space (although if you watch Star Wars Rebels, it certainly does imply that Jedi don't need spacesuits, at least for short trips).
Rey could also be descended from some other SW canon character that no one thought of, such as an Imperial character. Maybe Palpatine had children of his own and could be her grandfather. Maybe she's Padme's very-much-younger sister, since we know nothing about Padme's family on Naboo. There's a lot of territory to choose from without making her a relative of the Skywalkers. Okay, so Padme would make her a relative. Let's just not make her a sibling or descendant of the surviving Skywalker clan, okay? Are you listening, J.J.?
If there isn't a good explanation for her abandonment on Jakku, I hope that there is at least a thorough one. As I've grown older and watched more Star Wars material, especially The Clone Wars and Rebels, I've come to realize what a lot of other people also think: that the Jedi had become self-righteous jerks by the time of The Phantom Menace. They weren't meant to be a military organization; they were supposed to be more like a monastic organization that gave altruistic aid. Part of what Palpatine did, besides drawing Anakin to the Dark Side, was make the Jedi Order into a military unit and give them command of armies when they had no background for that sort of thing. Their biggest failing was that the Jedi Council didn't say no to any of this. So it isn't hard to accept that someone coming from that history could put a young child in hiding on a rough planet thinking she'd be safer there and then completely fail to check in on her. People are fallible creatures, even Force-using people. Who left Rey on Jakku doesn't necessarily have to have anything to do with who her parents were.
In any case, I'm really hoping that none of the theories listed in the article are true. I hope Rey isn't related to any existing characters, let alone the Skywalkers. I want the filmmakers to surprise me, and surprise me with something that makes such good sense that I'll be amazed I didn't think of it before. Is that too much to hope for?