The Guardian only looked at coverage from the past 18 months. If you looked at the 15-20 years Kate's been in the public eye, there have been plenty of 18-month periods where the coverage has been mostly negative. This isn't one of them, because she's done an excellent job in role she chose to take on, and the press eventually got bored with trying to find things to criticize when there really weren't any. The same would have happened with Meghan had she behaved the same way as Kate. There were far worse things said about Camilla than about either Meghan or Kate for decades, and basically no positive coverage until fairly recently. Is it fair that marrying into the royals requires enduring that? No, but it's not unique to Meghan, and it shouldn't have come as surprise. If she was truly unaware that the press could be that bad, that's her own fault for not having bothered to look into how previous royal brides were treated by the press.
Harry's far from blameless here, but if he'd set out with the intention of quitting the royal family because his wife didn't like it, he'd have just married Chelsy Davy or Cressida Bonas and done that to begin with. Meghan is getting blamed because she incorrectly assured him that she could handle it when, by her own words, she had no idea what would be involved. Now that he's married and has a baby, she's decided she doesn't like it anymore, and put him in a situation where he has to choose - and where there's basically no right answer. Harry's responsible for his own actions, but Meghan's responsible for creating the situation.
I'm not sure what you wanted the queen to do by way of support. Issuing public statements of support for royals being pilloried by the media for various perceived offenses against fashion and the status quo isn't the way it's done - she hasn't done it for anyone else, and if Meghan believes it should have been done for her because she's special, that's just further proof of what her detractors have said about her. It's not the queen's fault that Meghan's relatives are so much worse than Kate's or Camilla's or anyone else's. The queen isn't going to tell Thomas and Samantha Markle to stop saying mean things about Meghan, because it would be wildly inappropriate for her to publicly insert herself into someone else's family drama that doesn't involve her. Even if she did, does anyone seriously think that would have made them stop doing it? Meghan should have understood that. If she didn't, that's her own shortcoming, not the queen's.
No one would have cared all that much that they wanted to effectively retire early from royal life, but that's not what they did. Instead, they announced a "have their cake and eat it too" arrangement as thought it had been decided, when it hadn't been and wasn't up to them to decide. There was no good reason to do that, and I'm not sure how anyone can take anything either of them says seriously after they shamelessly lied to the public like that.