I agree that we did need more on Snoke, but I think his death was pretty well done. Snoke was essentially a red herring. He was the puppet behind turning Kylo Ren, but this story is very much about the problems of Masters, of Jedi and Sith, and we see how Luke failed his student, which lead to him turning, and Snoke being a Sith, is just there to treat Kylo like crap all the time. Kylo's conflicted ideas is what leads him to turn on Snoke and I think goes to show that Snoke was just being far too overconfident, much like Luke who thought he could bring the Jedi back, before getting a dose of realism that the ways of the old Jedi just don't work and their overconfidence lead to their downfall, as seen with the Prequels. This story isn't about Snoke and his plans for the galaxy, it's about Kylo Ren's rise and what I assume will be his fall. The good thing about a trilogy, is that I feel like they could start the opening of the next one with Kylo's involvement with Snoke, explain him a little more and fill in the missing gap pretty easily.
I couldn't disagree anymore with you on Rey. I think her use in the movie is great also. She's anything, but a Mary Sue. She makes mistakes, she's inexperienced, she gets drawn in by Snoke's trap, she's barely making it by in the Praetorian Guard battle, she's a useless rag doll in comparison to Snoke, she's clearly a natural with the force, but not enough to beat Kylo. I brought this up before, that while people expected differently, her parents reveal is actually well done in terms of the story and her character development. Sure, it was made to seem like a big deal, but in terms of the story itself, the idea that as a young girl, she was so distraught by the trauma of being abandoned by her parents, that she created a fantasy that her parents had just left her behind for some mysterious reason, makes a lot of sense. This kind of thing really happens. I can understand the disappointment that she wasn't a Skywalker, or Solo, or force baby or whatever fans thought up, but in terms of what this story delivered, it's really well done and I think almost works to turn her when Kylo is wanting both of them to join up as a way to deal with their problems. As a character moment, it's great. That it wasn't something crazy important, to me, shouldn't be considered a big negative.
As for Luke, I'm going to sound like a broken record, but the reveal that he wasn't actually on the planet is amazing. I see him dying being a mixture of things. He's old, worn down, there's no way he could fight Kylo, he couldn't even fight Rey (Which her abilities came from what she taught herself with her metal pole back on Jakku, and natural force strength, with that being her weapon training, so that works), and that he probably doesn't WANT to fight Kylo, so he uses his immense force powers for one last thing to help try and redeem himself, which is to help the resistance, and say goodbye to his former pupil with the knowledge that the Jedi will live on in Rey at least. The sheer strain of what he did, which is a crazy cool ability that I think makes plenty of sense in the Force, combined with the relief, let him give himself to the Force, exactly like Obi-Wan did.
But there are some issues with the other plots, I can agree there, though I think it's mostly just a problem with Finn/Rose and their section with the code breaker. That whole thing needed to be reworked and I feel like it could've been done more easily if it was just Poe, Finn, and Rose sneaking aboard Snokes ship to take out the tracker, cutting out the other planet trip entirely.
I feel like after setting aside actual issues in the movie with a few parts, it comes down not to an issue with a movie in particular, but an issue with expectations. The story not coming together how you thought it might doesn't make it a bad movie. With another watch, perhaps try to look at the story again from what they are wanting to offer, see if that shifts things. Maybe your view might change, maybe not, but I think there's a lot of good in this movie.