Personally, I like ending the story with Return of the Jedi, because it’s such a satisfying conclusion that I don’t think any continuation could ever truly live up to it, not even the EU. However, if I wanted to continue the story after Return of the Jedi, I think the best way to do it would be to create a new six-film saga rather than another trilogy. A Sequel hexalogy would give the story much more room to breathe and allow the new conflict to develop more gradually.
I don’t have anything against the idea of one of Luke’s students falling to the Dark Side and bringing the New Jedi Order to the brink of extinction, as long as the Jedi aren’t completely wiped out and, most importantly, the student who falls isn’t another member of the Skywalker family. There shouldn’t be any more Skywalkers falling to the Dark Side. Anakin’s fall was already tragic enough, and I don’t think the Skywalker family needs another tragedy of that kind. Also, after everything they went through because of Anakin’s fall, I think Luke and Leia would do everything they could to make sure their own children stayed on the right path.
So if one of Luke’s students has to fall to the Dark Side, I’d much rather it be an original character. The main protagonists could then be the children of the original cast.
I also don’t have anything against the idea of Luke going into exile and distancing himself from everyone for a while. What I don’t like is the idea of him doing it because he feels guilty about one of his students falling to the Dark Side. I think it would be much more in character for Luke to voluntarily withdraw from the galaxy so that he can meditate, reconnect with the Force, reflect on his mistakes and search for answers. Then, once he has found those answers and the right moment comes, he would return to the fight.
So, I’m not necessarily opposed to bringing the galaxy back to a status quo that resembles the one from the Original Trilogy. I just think you would need to actually earn that status quo. You could have the first trilogy show how the galaxy gradually falls back into a situation resembling the one from the Original Trilogy, and then use the second trilogy to show how the characters finally manage to get out of that situation. That would give the Sequels a much stronger sense of progression, which is something you can’t have if you begin the story after the tragedy has already happened.
And even then, I don’t think the New Republic should be completely destroyed. It could be reduced to a small handful of worlds and severely weakened, but I don’t think it should be wiped off the map entirely. The same goes for the New Jedi Order. It can be devastated and reduced to a small number of surviving Jedi, but there should still be something left to rebuild. That way, the Sequel saga could explore both the collapse and eventual restoration of these institutions without completely undoing everything that the Original Trilogy accomplished.