As for Luke: When has despair ever been his issue before? Even when his friends were trapped, the emperor was sitting over him and his father was fighting him, he fought off despair and hoped. It was so uncharacteristic of him. Doing that to a character without us, as the audience, seeing the reason for the change didn't feel like an assassination--it felt like watching someone's dislike being poured into the character and it becoming cancerous. I mean, I genuinely would have guessed the person who wrote Luke did not like him as a character and wanted to completely warp the attributes that made him the character he was. Luke is literally "A new Hope"--his character is designed around hope. Hopefulness has always been a central theme to the character. I mean, he was so hopeful he was naive, its why Han always laughed at him, even when he was a full on Jedi. And while its certainly an interesting story to see how hope changes to despair--it is a story no? To just have it happen feels really awful for the character. How can I connect with a character that I can't fathom the reasoning behind?
I mean, sense a sliver of good in my dark side wielding father who killed my family, destroyed a planet, killed my mentor, and was actively killing my friends--and stake my LIFE, and the lives of everyone important to me on the slim HOPE that I can change the overwhelming darkness in him......Vs....Murdering an innocent child at my despair that he will grow up and possibly be bad because I have no hope of affecting the sliver of darkness in him.
Secondly, about Rey's parentage. I totally agree, a shire-folk story would be fantastic. But Rey is not a Hobbit. Rey is an Aragorn. The thing that made the shire-folk so amazing is they were innocently naive and inept. Portions of the first (And second) book was spent on them dealing with the fact that they were so woefully weak, and way out of their element--at every turn during their "first act" they needed to be saved and helped, from Gandalf, to the Strider, to Tom Bombadil, then on to the Fellowship (One of the themes is how vulnerable they are to Boromir's corruption because they rely on the strength of the people in the fellowship so much). They, themselves, mention how small and weak they are, they hold knives in their hand and realize they can't use them, they see the world and realize they don't know where to go, they are brushed aside as pathetic by enemies and hide behind the "Captains" of the world (Boromir and Aragorn--this was a scene in Moria, that line was specifically used). And this is literally why the Hobbits were the foil, its an unexpected strength, but that lack of expectation came from them literally being weak until they were molded by need.
And then....their mentor dies. They are taken or forced to leave, and you see all the little lessons they learned while they were helpless have made them stronger as they are tested on their own. It feels natural by the time they are stabbing Nazgul's, or fighting at the gates, or killing Shelob--these characters have genuinely earned their bravery and skills. They hid behind their teachers, they were tossed around and shown to be useless, and from those experiences got stronger.
Did Rey do any of that? Did she have a moment of doubt and pain where she realized how small she was, and was saved by someone else, and had a goal set to become better? Did she ever get tossed into a situation that was beyond her, and saw the greater world she had to master (The internal shift of a heroic journey?)...Or did she simply walk into most situations with the tools and abilities to overcome them, developed on her own? Rey doesn't feel like a shire-folk. She feels like a Captain of the world, she's more Aragorn being convinced he's a king, than a hobbit discovering the world they need to grow into. Throughout the whole first movie it genuinely does feel like Rey is remember the strength "in her blood"--why she's a knight/lord/king, like Aragorn, not the Hobbits. The whole first movie seems a lot more like Rey coming to grips with who she is, and her powers--rather than being forged into a hero.
Which is why Rey being from no-where doesn't work. If Rey had been made out in the first movie to be scared, and incompetent, and bewildered by the enormity of what she did not know, this movie, as Rey finds herself and solidifies what she needs to deal with that, would have been fantastic. Could have easily accepted she came from nowhere. But the entire first movie wasn't that...Which is why it felt like a twist for a twist's sake. Plot elements need to have consequences. Rey is a junker from nowhere, and can speak every language, fly starships as well as ace pilots, and defeat a dark knight in a saber fight, use every Jedi trick we know, and is genuinely amazing....How? Why? What has she gained on this hero's journey? The whole "Journey" seems more about convincing her of her nature , than her growing into a hero. And that kind of story line lends itself to the Aragorn's of fiction, discovering who she is and why she is needed, rather than what she can become and how that is needed.
It genuinely felt like it was from writers that couldn't stand to have "their baby" thought of in ways the story needed. Maybe I'm wrong, but this all didn't sit well with me at all. People were discussing Rey's parentage for a reason. It felt like the writers wanted to do a "what a twist" and play a little joke at the questions, without actually wondering why those questions were being asked--like what made people believe that. Which is why I think you'll find a ton of people walk out of this saying "it was a great movie and I feel unsatisfied". This movie on its own is great, but when you start to digest the characters, you realize how hollow it all was.