What they did what make the movie about the characters, not the events around them. The PT is a story about the Fall of the Republic, the Destruction of the Jedi, and the turning of Anakin Skywalker. Its a three part series of events. It isn't so much about the character themselves, but about what happened around them. The events were predetermined by the OT, so they had to have them marked off at plot points even when they didn't quite makes sense. (they eventually expanded on the events to tell character stories in The Clone Wars cartoon series, which actually helps the characters make more sense)
The OT was about the characters and introducing the world to this universe through them. It wasn't about the events since those were not predetermined by a pre-existing set of films. The characters and the audience are learning about things at the same time.
The ST is still in production. We don't know were they are going to go with it yet. We have one finished film. A trailer for a second, and a theoretical release date for the third. What we've been given is a tale about the characters and how they interact with the universe that we, on some levels, already know. So it is more about the characters than the world building for Episode VII. The trailer for Episode VIII suggests that there will be more world building now that we know the characters. Now that the situation is different from what was expected. The situation in Episode VII was more or less what was expected, until Starkiller Base blows up the Republic capital planet's system from halfway across the galaxy. The aftermath of that will be where world building takes place. Before that the situation is "normal". We know what the Republic is...we saw that for the PT. We know the Resistance is like the Rebel Alliance because its Leia and they got X-wings. Check. The First Order is clearly some left overs from the Empire that are trying to make a move, with Leia getting in their way. Those are expected situations given what we know in the previous six films. Nothing radical is added to the mix that is not covered by the opening crawl or some dialog in the film. The aftermath of Starkiller Base is not presented yet because that should be in The Last Jedi, as that makes sense.
As for Han being dead, that's both Ford and Kasdan's, plot point they wanted back in Return of the Jedi. They probably would have gotten Ford back at all without that death. And it is likely that his death will have meaning in The Last Jedi. Luke's Jedi Order being massacred will be covered in The Last Jedi, now that we have Luke in the story again. Luke may not have gone all Yoda/exile. He was searching for the First Jedi Temple. It may well be that he's trying to find out why the Order keeps falling. What is wrong with the Jedi Order. Why must it end? Why does Luke seemingly want it to end? Is there more...something greater? As for Fisher's death, that was unforeseen, and cannot be blamed on the writers. What they do with Leia will be what they can do given what they could get from the actress before her death, and being respectful of her family.
