I feel like this is the real problem. It's not so much that people hate Rey, as much as it is that they hate the poorly-written movies she's in, and she's not really all that interesting character in her own right, so she becomes the target. She's effectively become the living avatar for people's disgust with the sequel trilogy as a whole.
It's the same way that a lot of the dislike and disgust with the prequel trilogy (but especially The Phantom Menace) crystallizes into "Jar-Jar is terrible! He's completely ruined the entire movie!" Yes, he's bad, but a lot of the pure hate against him is just misdirected hate over how terrible The Phantom Menace is as a whole. We could probably say that the pure venomous hate that Jake Lloyd and Hayden Christensen tend to get stems from the same sort of impulse.
It's a quirk of human psychology that we always look for villains to blame when things go wrong. We LOVE scapegoats, because it's always easier to blame a single person or group rather than trying to deconstruct systemic flaws and complex interactions.
If Rey was a more interesting character, people would probably transfer their dislike for the sequels to someone else (probably Finn), but because she's kind of bland, she makes a perfect target.
This is the thing people forget when they try and use the "Well, Luke was kind of boring too!" defense for Rey. The difference being, the original films were actually GOOD, and they also had Han Solo to distract us all from whatever flaws were there because he was being awesome enough for everyone.
Jar Jar goes out of his way to be annoying though, I mean if you cut him out of that movie entirely it probably gets a good bit better. He is a pointless character meant to sell toys to kids and make kids laugh, he's like an Ewok but cranked up to 11.
Rey's biggest problem is she is a Mary Sue, but hate to say it but in the world of Force users nearly all the super powerful ones can do force shit easily. Luke didn't get a ton of training to become a powerful Jedi either.