This has been said probably a trillion times on here, but 7 and 8 link together just fine.
I still disagree, for a number of smaller reasons, but also for one fundamental reason: the treatment of Luke in TFA. TFA makes finding Luke the central object of the whole film. The heroes and villains are both obsessed with this end goal, and both speak of it as a massive game-changer that will determine the course of the war. Snoke is deeply concerned about stopping Luke’s return so that he can’t train a new generation of Jedi, despite Luke exiling himself to an island willingly and wanting to die. Leia, despite having led the war by herself thus far after Luke and Han both abandoned her, is convinced that finding Luke will turn the tide. There’s also a map pointing to Luke for some reason, despite Luke not wanting to be found. The opening crawl of TFA even implies that the First Order rose to power largely because of Luke’s absence.
So, the whole of TFA chooses to center itself around Luke, hyping up Luke to the audience and stressing his importance in shaping the course of the war. The movie tells its viewers that Luke leaving was a huge deal to the galaxy, and that Luke returning will also be a huge deal. Luke is just one person, but the movie makes him out to be a larger-than-life hero (which he never was in the OT. Luke was always much more human than that.) who could reshape the galaxy. Someone who is extremely important to both the good guys and bad guys for what he could potentially do.
JJ Abrams even wanted the movie to end with Luke surrounded by floating rocks, to wow the audience by showing off how powerful Luke was.
Then in TLJ, the movie “defies expectations” by pointing out that Luke isn’t actually the larger-than-life superhero TFA made him out to be (of course, TFA is what established that expectation in the first place), and goes in the extreme opposite direction to paint him as an impotent failure who wants nothing to do with the galaxy. Which raises the question: why did they bother hyping up Luke so much, then telling the audience they were wrong for getting excited about Luke? Perhaps it was all part of the plan from the start to “mess with audience expectations”, but that doesn’t explain JJ wanting to show off Luke’s power at the end of TFA. More likely, JJ and Rian just had conflicting visions for the role they wanted Luke to play in the trilogy’s story.