Crabby old Luke is a million "old master" characters from a million different films, and for a guy who was supposed to have been the most powerful Jedi in the galaxy, it's surprising how much he sucked at his job. Just like Obi-Wan and Anakin, Luke couldn't save Ben from the dark side, and just like Obi-Wan, he becomes a hermit, and eventually meets someone connected to his failed pupil, who he can educate successfully, before dying, in this case, a truly pathetic death, by remote control. As has been pointed out, not only did he repeat the same mistakes his master did, but he also retreated into whiny little bitch mode for no reason, either. Luke, who grew so much as a person in the original trilogy, here disappeared to an island to shirk his responsibilities until he was shamed into action by the first person to come along. Why? Luke had Han and Leia, Luke had R2-D2, C-3PO and Chewbacca, and he had a responsibility to protect them from what would become Kylo Ren and the First Order. But of course, Johnson and Disney don't care about Luke, because he's here for fan service, to get the older asses in the seats, along with his sister. The same could be said of Han Solo and The Force Awakens, because Han was basically in that movie to ejaculate and die. Now, by proxy, we're all supposed to care that much more about what happens to Kylo/Ben because of his bloodline (Aha! There it is!), and once Abrams had established that relationship, why not dispose of the older character by having him killed?
(As an aside, just personally, I would have loved to see Luke get off the damn island for a bit. Like many people, I was hoping for a Han/Leia/Luke reunion, if only for a short while, but The Force Awakens mortally wounded that idea, and now The Last Jedi has really delivered the death blow.)
And I would suggest that Rey's bloodline matters just as much if not more. It's mattered for two films of this trilogy, and it matters to her, personally. And in any event, she came to her present station by dumb luck, which is otherwise known in most films as "destiny", which isn't exactly a merit-based system. The statement that her parents might be "nobodies"--a dubious assertion, considering it came from Kylo Ren--isn't really enough to say that The Last Jedi isn't concerned with bloodlines. Remember, also, that Luke casually mentions that Ben Solo took some of Luke's other students with him as he left. Ostensibly, these people are at least semi-powerful Jedi-in-training, and where are they? Have they been killed? Are they in the First Order? No, they're nowhere, that's where, because this trilogy, like the previous trilogy, is becoming all about one "bloodline", and this is emphasized through the intriguing "force link" that Rey and Kylo have, as well as the fact that Rey and Finn don't even see (and barely even mention) each other again until the end of the film.
The other things you mention: Long-shot missions: Doesn't the Resistance end up in another one of those, anyway? Don't, Rey, Kylo, Hux, Poe, and especially Finn and Rose end up in ludicrously dangerous situations where they should die, but miraculously survive? Of course, Vice Admiral Holdo isn't nearly as lucky, and Johnson even disposes of Admiral Ackbar, but then neither of them were in their twenties or thirties, and the young audience isn't likely to be pining that hard for a Laura Dern doll, are they?.
As for characters being good or evil, you can draw fairly exact parallels between Luke in The Empire Strikes Back and Rey, as well as Kylo and Vader/Anakin in Return of the Jedi, right down to Kylo killing Snoke to [strike]save Rey[/strike] overthrow him. As for the timing of this, that's down to the writers, and if they know what they're doing. For myself, the way the scene was structured and set up, along with how it was drawn out and eventually dragged on, made it painfully obvious what was going to happen. After all, I doubt Disney/Lucasfilm would have sanctioned killing Rey in such a deliciously evil fashion.
And this is where the corporate agenda comes in. First of all, the series has a taste for blood regarding original trilogy characters that is all but absent from any of the new characters. Han sacrificing himself is okay, but now Leia is dead in real life, and then The Last Jedi comes along, and ends with Luke "fading away" a la Obi-Wan in Star Wars, which in all likelihood, means he's dead, as well. And I'm sorry, people can fall back on "Force Ghosts" as much as they like, but Star Wars isn't Ghostbusters or The Frighteners, so either Episode IX is going to feature an extremely odd tonal shift, or Disney is pushing the audience to dispose of the Skywalker saga and get used to the franchise without the characters they have loved for decades. I was ready for that in Episode IX, but I certainly would have preferred that two or all three of them survived, and their ultimate fates were left open-ended. It seems very dismissive to blot out these heroes simply because they've gotten old--you would think our present generation would have a bit more sense, if not sensitivity, than that.
On the other hand, all of the new, young characters (read: new toylines) seem invincible. Perhaps one of them will die to end the trilogy (likely Poe, if I had to guess), but it does seem interesting that in spite of so many new characters coming in, all of them, in this dangerous, wartime situation, are allergic to death. The original trilogy sort of suffered from this, at least we had the whole "frozen in carbonite" thing to keep people guessing for a while.
I guess I could go on, but to be honest, I'm tired.
have gone the way I wanted, but I could accept that if the films got to their destination down less well-traveled paths.