With the Emperor, the backstory we got was, "The Emperor has dissolved the Senate. The last remnant of the old republic is now gone."
Sure, with the First Order and Snoke I'd like a couple lines, something like Hux proclaiming, "Our Supreme Leader found the quivering remnants of the old empire and forged us into a sword that has cut through our enemies on a hundred worlds," but that would be enough. How big is the First Order, was Snoke part of the empire or an outsider, and maybe a few other tidbits to provide contour for the personal stories of the characters.
Not really comparable, though. When we saw Star Wars for the first time, we had no background for the GFFA, so we could easily just accept the existence of an Empire that had, a generation ago, replaced the Republic, and an Emperor that had just dissolved the Senate.
Now, we know that the Empire was defeated and the Emperor killed 30 years ago, and that the Emperor was the most powerful dark side force user around. We know about the Sith, and the "rule of two," and that both of them were killed. We know that the Empire was the culmination of generations - perhaps thousands of years' worth - of sith machinations.
So, if you open the window 30 years later to show us another super-powerful dark side force user at the head of another (or maybe the same) galaxy-dominating army of space nazis, you really have some explaining to do. We saw the rebel alliance, with our heroes Luke, Leia, and Han, solve all these problems before. Now we're being shown our three heroes as a bunch of losers (a failed teacher who quit and went to pout for the last decade; a would-be patriot that was forced out of government, get her resistance movement decimated, and whose 'allies' abandon her in her moment of need; and a hustler on the run from pretty much everyone who left his wife and gave up on his kid, who tries to reach out to that kid and gets skewered and dropped down a hole by that kid.) We're being shown that they really might as well have not bothered, because the Sith Lord and his Space Nazis seems to be stuck on repeat.
I mean, I approached Ep 7 with enthusiasm. I didn't know what to expect our heroes to be up to 30 years later, but what I did not expect was to find them miserable, wretched, and pathetic. Ok, so they killed Han. I know they were talking about that in Ep 6, so it's not a huge shock. Surely that sacrifice will motivate Luke to get off his ass and join Leia, and surely Leia will be a beacon of hope around which the galaxy can rally, right? Nope. Welcome to Ep 8, where Leia proves to be the worst military commander ever, and where Luke is a whiny, self-absorbed failure. When he does snap out of it, he manages to be a badass for a couple of minutes, which is too much for him to handle and he just dies because reasons.
I digress.
My point is that we're not starting with a blank slate. We've got a galaxy far, far away that we left with the biggest problems solved and established heroes in their prime to tidy things up. If you start the sequel trilogy with "everything has gone to hell" I think you have to really do some work to explain why and how that happened.
And to those of you who argue that we need to move on beyond the Skywalkers and not focus on that legacy, I can see the appeal of that. I used to share that idea, too. The thing is, you can't move forward if you start by crapping all over the past. If your starting point invalidates everything - literally everything - that the last generation of heroes accomplished, you have to restore that legacy before you can leave it behind. I mean, you clearly don't
have to, but restoring the Skywalker legacy is, I think, something that has to be done before my generation is going to be willing to leave it behind. At this point, the only way I can see that happening is Rey Skywalker.
Han, Luke, and Leia fixed the galaxy. Rather than introduce a new challenge for the next generation to overcome, JJ and Rian decided to just invalidate and erase those fixes. That has to be justified, and whatever fixes the galaxy this time needs to come from the OT heroes, even if indirectly through their inheritors in this next generation. Otherwise, you're just flinging poo at those of us who grew up with Luke, Leia, and Han, trashing our heroes just to make Mary Sue and Darth Emo seem more impressive.